First, I suspect that the Rams can resign Shelton for at least 1 year for about the same as it would cost for a 2nd round pick (maybe a 1st).
I thought Shelton did a really good job for the Rams but I doubt he'll draw a big dollar offer. So, it would be one thing to draft a Center later to develop or maybe as an immediate back up, but another to take one that you pencil in as an immediate starter.
I wouldn't like to see the Rams address any Oline, QB, ILB, or RB until at least the 3rd round. The Rams need at least 2 starting potential Corners, and I suspect that those guys will be there if the Rams stay put in rounds 1 and 2.