I may have posted about this before; if so, then apologies, but it's worth revisiting.
By "roots rockers", I mean those bands and artists who carry their influences on their sleeves for everyone to see and pay their loving respect...as well as some who add a few twists to make things interesting.
And I don't mean clones, but those who draw inspiration from older music: blues, early rock n' roll, jazz, r&b, etc. Often, they stick to their guns regardless of trends, because, if it ain't broken, then why fix it?
Some notable examples:
J. Geils Band (r&b, soul)
Black Crowes (blues, r&b, soul)
Los Lobos (americana, tex-mex, early r&r)
Grateful Dead (early r&r, bluegrass, folk)
Little Feat (new orleans, r&b, blues)
Traveling Wilburys (country, heartland)
Blues Traveler (blues, americana)
And some more recent, though excellent, examples:
Wilco (americana, folk, country, heartland)
Deer Tick (early r&r, folk, country)
Calexico (tex-mex, americana)
Bright Eyes (folk, country)
Ben Harper (folk, blues, gospel)
Patty Griffin (folk, gospel, americana)
P.S. In terms of newer music, with a few exceptions, this generally the stuff I go for: mature sensibilities with respect for traditions but a willingness to shake things up and maybe add a little psychedelia, hard rock, or jazz elements to keep it lively and make it fresh.