Let's get to the tweet:
That's NFL.com's Ian Rapoport, so I'd bet this is legit. If so, the Rams have added a pretty solid piece to their interior defensive line strengthening the best unit on the team. There's a position switch coming here though as Carrington played 3-4 end for Buffalo and would move inside for the Rams.
It would also likely throw out some scenarios in the 2014 NFL Draft in which the Rams take a DT early. Having recently picked Arizona St. DT Will Sutton for a Twitter-based mock draft, I acknowledge the position need was there. And while there's still an argument to be made that the Rams are going 100% best player available with every pick, the likelier result is that the Rams look elsewhere on days one and two.
There's a question of rotation now on the Rams' interior defensive line. Carrington is coming off of an injury-marked 2013 season in which he tore his quad tendon having been appointed the week one starter in the preseason. The Arkansas State product has come along, but you'd assume he'll be splitting time between Michael Brockers and Kendall Langford.
In any case, the Rams have put another piece together in the puzzle that is the 2014 roster if Rapoport's source holds true.