Fullback Michael Robinson Tweeted a little while ago that he is indeed back with the Seahawks:

That apparently means he will be on the field today when the Seahawks practice later this afternoon.

No corresponding move has yet been announced, but the team is signing Robinson to fill in at a fullback spot where he has no healthy players at the moment with Derrick Coleman ailing with a hamstring injury and Spencer Ware out since game two with a high ankle sprain.