My second thought was to try and resign A'Shawn Robinson. He hasn't been very popular on the market either. The Rams can create a few bucks pretty easy if they wanted either of these two back.
A'shawn is a solid pro, he is only 27 and plays the run pretty well but offers very little in the pash rush side. Sad thing is he has as much natural talent and gifts as anyone but he just doesn't show up like he should. I still like him as a player and think he would be a good fit as a Ram moving forward.
It's my opinion both would help the team next year. Johnson is a perfect fit at safety for the Rams and the D they play. Put him next to Fuller and the Rams are suddenly very strong at the position if Fuller can hold up for the year.