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

Context paragraphs:
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.

Somebody Told Me: "Somebody Told Me" is a song by American rock band the Killers.  It was released as the second official single from the group's debut studio album "Hot Fuss" (2004), and was written by band members Brandon Flowers, Mark Stoermer, Dave Keuning and Ronnie Vannucci Jr..  In an interview with Rolling Stone, Brandon Flowers said "This is the story of trying to meet someone in a club."  It is written in the key of B-flat minor.

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.

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.

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.

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.

Dragonheads (EP): Dragonheads is an EP by Finnish folk metal band Ensiferum.  It was released on February 15, 2006 by Spinefarm Records.  It is the first Ensiferum release featuring the then recently hired members Petri Lindroos, Sami Hinkka and Janne Parviainen.  Mastered at Finnvox Studios.  "Warrior's Quest" and "White Storm" are the re-recordings of songs from the band's second demo.  "Finnish Medley" is a medley of the Finnish traditional pieces "Karjalan kunnailla", "Myrskyluodon Maija", and "Metsämiehen laulu".

Ted Sablay: Theodore 'Ted' Sablay (born April 18, 1976) is an American guitar player, keyboardist and music teacher.  He has been a touring musician for The Killers since 2006.  Sablay has played piano on "Romeo and Juliet" on the band's compilation album "Sawdust," engineered sessions for the Killers' 2008 album "Day & Age", and worked as a music consultant on "Flamingo", the 2010 solo album by Killers singer Brandon Flowers.  Sablay was formerly in the Las Vegas bands Attaboy Skip and Expert on October alongside Ronnie Vannucci Jr. Sablay has contributed bass to Vannucci's side project Big Talk and Flowers' second solo album, "The Desired Effect."  In 2017, Sablay was picked to fill in for Dave Keuning on lead guitar during live dates supporting the Killers' album, "Wonderful Wonderful".

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.

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.

Supporting paragraphs: Petri Lindroos Brandon Flowers
Answer: lead singer