Robinson's contract is fully guaranteed. Cut him and the Rams have several millions dead cap space. Clearly, if they feel that he's just not going to make it even as a backup, then cut him. But he costs the same on the team as off.
Considering how incompetent Fisher's offense was, and that they developed absolutely NOBODY on offense during Fisher's tenure, then it is certainly worth a try to give an entire new group of coaches a shot at a man with that much physical talent. That he might be weak minded or emotionally immature doesn't mean he can't be a serviceable player in the right hands.He could well make a good pulling Guard. His speed and size and agility would be formidable.