Roger Arntzen (born 3 June 1976)[1] is a Norwegian jazz bassist, known from playing in bands like In the Country (trio), In the Country with Knut Reiersrud and Solveig Slettahjell, Ballrogg, Chrome Hill, One Small Step, John-Kåre Hansen Northern Concept and previously also with Håvard Stubø Trio and the band Østenfor Sol.

Through his projects he has worked with downtown NYC icon Marc Ribot, Bob Hoffnar, Josh Abrams, Toto Alvarez, BJ Cole, Michiyo Yagi, Tamaya Honda, Noritaka Tanaka, Tetuzi Akiyama, Neil Metcalfe, Terry Day, John Russell, Frode Grytten, Susanna Wallumrød, Frida Ånnevik, Tore Brunborg, Stian Carstensen, Bugge Wesseltoft, Mathias Eick, Odd Riisnæs, Lars Klevstrand, Moddi, Thomas Dybdahl, Steinar Ofsdal, Kari Svendsen, Jon Arne Corell, Alf Cranner, Göran Fristorp among others.

He picked up playing the accordion at five years of age, changing instrument to the tuba when he was at high school.

In the Country has been active since 2003, releasing nine well received albums, This Was The Pace Of My Heartbeat (2004), Losing Stones (2006), Collecting Bones (2006), Whiteout (2009) with Andreas Mjøs, Sounds And Sights (2011) with Andreas Mjøs, Sunset Sunrise (2013), Norwegian Woods (2014) with Knut Reiersrud, Solveig Slettahjell, Bugge Wesseltoft, Skogenes Song (2014) with Frida Ånnevik, Trail Of Souls (2015) with Knut.

In The Country was awarded "Young Jazz Musicians Of The Year 2004" in Norway and Down Beat called their debut album "one of the finest and most arresting albums to come out of Europe" that year,[2] while All About Jazz reviewer John Kelman has suggested Whiteout as a contender for the "best of" list for 2009.