I tried to watch as many clips as possible of Domata Peko from 2016.
It looks like his role was to be taken away from the play by either the center or the guard, leaving a huge hole in the middle for the RB to attack. He played that role pretty well. He extends his arms, the o-lineman blocks him and he goes wherever the o-lineman takes him. Peko's inability to disengage and try to make the tackle is impressive.
I guess that's the role he will play in Denver.