Question: What role with their bands do both Brandon Flowers and Petri Lindroos hold ?

full_context: Document 1: Eric Peterson (musician): Eric Peterson (born May 14, 1964) is an American guitarist. He is best known as the only constant member of the US thrash metal band Testament. Peterson has also formed a side project black metal band called Dragonlord, in which he plays guitar and also sings. In Testament, Peterson was originally a rhythm guitarist while Alex Skolnick handled all lead work. More recently though, Peterson plays leads along with Skolnick.
Document 2: Alexi Laiho: Alexi "Wildchild" Laiho (born Markku Uula Aleksi Laiho; 8 April 1979) is a Finnish guitarist, composer, and vocalist. He is best known as the lead guitarist, lead vocalist and founding member of the melodic death metal band Children of Bodom, and is also the guitarist for Sinergy and Kylähullut. He has previously played with Thy Serpent and Impaled Nazarene on occasion, as well as Warmen and Hypocrisy.
Document 3: The Killers: The Killers are an American rock band formed in Las Vegas, Nevada, in 2001 by members Brandon Flowers (lead vocals, keyboards, bass) and Dave Keuning (guitar, backing vocals). Mark Stoermer (bass, guitar, backing vocals) and Ronnie Vannucci, Jr. (drums, percussion) would complete the current line-up of the band in 2002. The band's name is derived from a logo on the bass drum of a fictitious band, portrayed in the music video for the New Order song "Crystal".
Document 4: Crossfire (Brandon Flowers song): "Crossfire" is the debut solo single from singer-songwriter and frontman of The Killers, Brandon Flowers. Written by Flowers himself, and produced by Brendan O'Brien, it is the first single from his debut solo album, "Flamingo". A video for the single was released on July 8, 2010, and features actress Charlize Theron.
Document 5: Brandon Flowers: Brandon Richard Flowers (born June 21, 1981) is an American singer, songwriter and multi-instrumentalist. He is best known as the lead singer, keyboardist and occasional bass guitarist of the Las Vegas-based rock band The Killers, with whom he has recorded five studio albums.
Document 6: Petri Lindroos: Petri Lindroos (born 10 January 1980 in Espoo, Finland) is a melodic death/folk metal guitarist and vocalist. He is currently the lead vocalist in Ensiferum and, prior to this, was a founder and lead vocalist for Norther.
Document 7: Flamingo (Brandon Flowers album): Flamingo is the debut solo studio album by American singer-songwriter and The Killers lead singer Brandon Flowers, released on September 3, 2010 by Island Records. It was recorded at Battle Born Studios in Winchester, Nevada, and Henson Recording Studios in Hollywood, California. The album debuted at number one on the UK Albums Chart.
Document 8: Markus Toivonen: Markus Toivonen (born 1979 in Helsinki) is the founding member of the Finnish folk/death metal band Ensiferum. Markus founded the band in 1995 and is the sole original member to have lasted the distance to Ensiferum's present incarnation. His role in the band is guitarist and primary songwriter. He has always contributed backing vocals and since the departure of Jari Mäenpää in 2004 has taken up a greater role behind the microphone, sharing the clean vocal parts with new bass player Sami Hinkka, with Mäenpää's replacement Petri Lindroos handling the harsh vocals.
Document 9: The Desired Effect: The Desired Effect is the second studio album by American singer/songwriter and The Killers frontman Brandon Flowers, released in Ireland on May 15, 2015, in the United Kingdom on May 18, 2015 and on May 19, 2015 in the United States. It was recorded at Battle Born Studios, Winchester, Nevada. It was produced by Ariel Rechtshaid and Brandon Flowers and mixed by Alan Moulder. The album debuted at number one on the UK Albums Chart, making it Flowers' sixth overall UK number-one record.
Document 10: Timo Kotipelto: Timo Antero Kotipelto (born 15 March 1969 in Lappajärvi, Finland) is the vocalist of the Finnish power metal band Stratovarius and is the creator and vocalist of the power metal band Kotipelto. Kotipelto is currently the longest standing member of Stratovarius, after the departure of Timo Tolkki.
Document 11: Jani Liimatainen: Jani Allan Kristian Liimatainen (born 9 September 1980 in Kemi, Finland) is a Finnish musician, songwriter and backing vocalist. He is the former guitarist and one of the founding members of the power metal band Sonata Arctica. He has also performed with Cain's Offering, Altaria and Stratovarius vocalist Timo Kotipelto (his band mate in Cain's Offering).
Document 12: Battle Born Studios: Battle Born Studios, located in the Winchester, Nevada, is a 2000 sqft recording studio owned by The Killers. The studio has hosted groups including Mötley Crüe, B.B. King, Elton John, The Killers, and Imagine Dragons.
Document 13: Aleksi Sihvonen: Aleksi Sihvonen is the current vocalist for the Finnish band Medicated. He replaced Norther's vocalist Petri Lindroos in 2009, until the group disbanded in 2012. He was also the former guitarist and vocalist of Imperanon.
Document 14: N (album): N is the fifth full-length studio album by Finnish melodic death metal band Norther. The album was released through Century Media Records on February 13, 2008 for Finland, and other dates in February for other parts of Europe. The track "Frozen Angel" from their previous EP, "No Way Back", was re-recorded for the album. "We Rock" and "Frozen Angel" have been made into music videos. This is also the last Norther album to have founding member Petri Lindroos on vocal and guitar duties.
Document 15: Brian Karscig: Brian Joseph Karscig is a musician, songwriter, and record producer, but is mostly recognized as the co-singer/guitarist/songwriter for the American Rock and Roll Band Louis XIV signed to Atlantic Records. He also is the singer/guitarist/songwriter of American Rock Band The Nervous Wreckords. Karscig owns Nervous Productions, and co-owner of "The Pineapple Recording Group", and has produced records for artists such as Anya Marina (Slow and Steady Seduction: Phase II) for Chopshop/Atlantic Records, The Silent Comedy, Transfer, Les Gars, Apes of Wrath, Republic of Letters, and Subsurfer. Aside from his songwriting with LOUIS XIV, and The Nervous Wreckords, Karscig is also known for his co-writes with Brandon Flowers of The Killers ("Thief in the Choir" and "Turn the Light On"), and Sam Endicott of The Bravery ("Send it in a Letter"), as well as Anya Marina ("Afterparty at Jimmy's) and A.J. Croce's 2013 single "Keep the Change". Karscig is also credited with additional vocals on The Killers 2006 release "Sam's Town". Most recently Karscig toured South America as the piano/guitar player for Brandon Flowers "Desired Effect" Tour, and also joined The Killers as 2nd guitar player for their 2016 US/Canada tour. Although The Nervous Wreckords was Karscig's solo effort after Louis XIV, Karscig started his first solo record under his birth name Brian Karscig due out early 2017.
ground_truth: lead singer