Question: Which mixed martial artist was represented by Marc Roberts?

full_context: Document 1: Tim Sylvia: Timothy Deane Sylvia (born March 5, 1976) is a retired American mixed martial arts (MMA) fighter, professional wrestler, and former two-time UFC Heavyweight Champion. He has competed as a Super Heavyweight and Heavyweight. While perhaps best known for competing in the UFC, Sylvia has also competed for Affliction, the International Fighting Championships (IFC), and ONE FC.
Document 2: Leigh Steinberg: Leigh William Steinberg (born March 27, 1949) is an American sports agent. During his 41-year career, Steinberg has represented over 300 professional athletes in football, baseball, basketball, boxing, and Olympic sports. He has represented the No. 1 overall pick in the NFL draft a record eight times. Steinberg is often credited as the real-life inspiration of the sports agent from Cameron Crowe's film "Jerry Maguire" in 1996.
Document 3: Roy Jones Jr.: Roy Levesta Jones Jr. (born January 16, 1969) is an American professional boxer, boxing commentator, boxing trainer, rapper, and actor who holds dual American and Russian citizenship. He is a six-time former world champion in four weight classes, having held titles at middleweight, super middleweight, light heavyweight, and heavyweight; and is the only boxer in history to start his professional career at light middleweight and go on to win a heavyweight title. As an amateur he represented the United States at the 1988 Summer Olympics, winning a silver medal in the light middleweight division.
Document 4: Aaron Goodwin: Aaron Goodwin is a sports agent who represents players in the National Basketball Association and Women's National Basketball Association. He was the initial agent for LeBron James, and negotiated endorsement deals paying James over $135 million, including a $90 million deal with Nike. James later left Goodwin in favor of agent Leon Rose. He was initially Kevin Durant's agent, but Durant moved to Rob Pelinka. Goodwin's other clients have included Dwight Howard, Chris Webber, Damian Lillard, Gary Payton, Jason Kidd, Shareef Abdur-Rahim, Vin Baker, DeMar DeRozan, Damon Stoudamire, Todd MacCulloch, Nate Robinson, and Candace Parker. In 2004, he was ranked eighth on "Sports Illustrated"<nowiki>'</nowiki>s list of the Most Influential Minorities in Sports.
Document 5: Ray Mercer: Raymond Anthony "Ray" Mercer (born April 4, 1961) is an American former professional boxer, kickboxer, and mixed martial artist. In boxing he competed from 1989 to 2008, and held the WBO heavyweight title from 1991 to 1992. As an amateur he won a gold medal in the heavyweight division at the 1988 Summer Olympics. As a mixed martial artist, Mercer is known for scoring an upset one-punch knockout victory over former UFC heavyweight champion Tim Sylvia in 2009.
Document 6: Roger Montgomery (sports agent): Roger Montgomery (born 1970) is an American sports agent and former professional basketball player. He is the current CEO of Montgomery Sports Group. As a sports agent, Montgomery has represented basketball players in the National Basketball Association (NBA) and international leagues.
Document 7: Frank Bruno: Franklin Roy "Frank" Bruno, {'1': ", '2': ", '3': ", '4': "} (born 16 November 1961) is a British former professional boxer who competed from 1982 to 1996. Bruno had a highly publicised and extremely eventful career. The pinnacle of his boxing career was winning the WBC heavyweight title, in what was his fourth world championship challenge. He also held the European heavyweight title earlier in his career. Bruno was one of the most well-loved and recognisable boxers in British history, and faced multiple top-rated heavyweights during his career including two bouts with Mike Tyson and a domestic clash against Lennox Lewis. He won the WBC title in 1995 after defeating Oliver McCall at a packed Wembley Stadium. Bruno was known for his excellent punching power: he won 40 of his 45 bouts and 38 by knockout, giving him a 95% knockout rate from the fights he won; his overall knockout percentage is 84.44%. Like Henry Cooper before him, Bruno has remained a popular celebrity with the British public following his retirement from boxing.
Document 8: Lamon Brewster: Lamon Tajuan Brewster (born June 5, 1973) is an American former professional boxer who competed from 1996 to 2010. He held the WBO heavyweight title from 2004 to 2006, and is best known for scoring an upset knockout victory over Wladimir Klitschko to win the vacant title. As an amateur, Brewster won the U.S. national championships in 1995, and a silver medal at that year's Pan American Games, both in the heavyweight division. Following his retirement from the sport in 2011, he became an entrepreneur and founded a consulting business.
Document 9: Hasim Rahman: Hasim Sharif Rahman (born November 7, 1972) is an American former professional boxer who competed from 1994 to 2014. He is a two-time world heavyweight champion, having held the unified WBC, IBF, IBO, and lineal titles in 2001; and the WBC title again from 2005 to 2006. Rahman first became known on the world stage in 2001 when he scored an upset knockout victory against Lennox Lewis to win the unified heavyweight championship. Lewis avenged the loss and regained his championship by knocking out Rahman in a rematch later that year. Rahman won the WBC title (initially the interim version) for a second time in 2005 by defeating Monte Barrett, after which the WBC elevated him to full champion status by the year's end. His reign as champion ended in 2006 via another knockout loss, this time to Oleg Maskaev in a rematch of their first fight in 1999.
Document 10: Don Yee: Donald H. Yee (born c. 1960) is an American sports agent and a partner of the sports talent agency Yee & Dubin. Yee mainly represents NFL players and coaches, most notably New England Patriots quarterback Tom Brady and New Orleans Saints head coach Sean Payton. He has been highly praised by media including "Sports Illustrated" and the "Washington Post" for his work in representing Tom Brady.
Document 11: David Falk: David B. Falk (born 1950) is an American sports agent who primarily works with basketball players in the National Basketball Association. Falk began his career representing professional tennis players for Donald Dell's ProServ and is best known for representing sports icon Michael Jordan for the entirety of Jordan's career. Besides Jordan, Falk has represented more than 100 other NBA players, and is generally considered to be the most influential player agent the NBA has seen. During the peak years of Falk's career in the 1990s, he was often considered the second-most powerful person in the NBA behind Commissioner David Stern, and in 2000 he had at least one client on all but two NBA teams. He was listed among the "100 Most Powerful People in Sports" for 12 straight years from 1990 to 2001 by "The Sporting News", and was also named one of the Top 50 Marketers in the United States by Advertising Age in 1995.
Document 12: Mike Tyson: Michael Gerard Tyson ( ; born June 30, 1966) is an American former professional boxer who competed from 1985 to 2005. He reigned as the undisputed world heavyweight champion and holds the record as the youngest boxer to win a heavyweight title at 20 years, 4 months and 22 days old. Tyson won his first 19 professional fights by knockout, 12 of them in the first round. He won the WBC title in 1986 after stopping Trevor Berbick in two rounds, and added the WBA and IBF titles after defeating James Smith and Tony Tucker in 1987. This made Tyson the first heavyweight boxer to simultaneously hold the WBA, WBC and IBF titles, and the only heavyweight to successively unify them.
Document 13: Marc Roberts (sports agent): Marc Roberts (born September 20, 1959, Newark, New Jersey) was a Division I basketball player at American University in Washington, D.C., before starting a career as a sports agent. He has represented NFL players such as Antonio Freeman, Tyronne Drakeford, O.J. McDuffie, Jerry Porter, and Tyrone Wheatley, NBA players Bobby Jackson, Johnny Newman, and Derek Anderson, and World Champion boxers "Merciless" Ray Mercer, Shannon Briggs, Tracy Harris Patterson, Danell Nicholson, Charles Murray and Alex Trujillo. He was one of the five sports agents consulted in making the film "Jerry Maguire".
Document 14: Matt Hannaford: Matt Hannaford is an MLBPA certified sports agent and partner at MVP Sports Group. Along with partner Dan Lozano, he represents some of the games biggest names in baseball, including Albert Pujols, Jimmy Rollins, Joey Votto, Josh Donaldson, Nick Swisher, Brian Wilson and Carlos Beltrán. Hannaford has also been responsible for recruiting some of the game's best young stars, including Manny Machado, Michael Taylor, Yonder Alonso and Derek Norris.
Document 15: Oliver McCall: Oliver McCall (born April 21, 1965) is an American professional boxer. He is best known for winning the WBC heavyweight title in 1994, after scoring an upset knockout victory over Lennox Lewis. The next year, he defended the title against Larry Holmes before losing it to Frank Bruno. McCall would also become known for an in-ring meltdown during his 1997 rematch with Lewis.
ground_truth: Raymond Anthony "Ray" Mercer