He sits!

Well, with some support. Dylan's much happier sitting than laying down, since he can see his toys and the world around him more easily. 

Rolling over progress seems to have stalled.  He's mastered rolling from front-to-back, but doesn't seem to think that back-to-front is worth practicing any more. He did it once and ended up with his arms pinned underneath him, so he likely figures that back-to-front rolling is for chumps.