Karl Johan Roger Tallroth, born in 1958, is a Swedish folk musician and composer, best known as a member of the band Väsen. He was educated at the Sjövik Folk High School and the School of Music in Örebro University. Principally a guitarist, he also plays other stringed instruments such as the bouzouki, ukulele, mandola, mandolin, fiddle, viola, oud and double bass. He also works as an arranger, and teaches at both the Royal College of Music in Stockholm and in Örebro University.
In groups such as Väsen, Tallroth has created a personal playing style which often includes alternative tunings (especially A-D-A-D-A-D on the guitar) and distinct rhythmic patterns.
He has worked with musicians such as Annbjørg Lien and Sofia Karlsson, and collaborated on the theatrical production Hästen och tranan.