I have read where Rosario is not a good blocker. IMO this puts Williams ahead of Rosario. If you are going to play TE you need some decent hands but you have to be able to BLOCK. This is exactly why Barnidge didn't see the field very much.
Olsen and Hartsock are locks. I would be shocked to see Hartsock gone.
IMO Brockel's versatility to fill either the fullback role or Tight End is going to make it tough to keep Rosario or Williams. Williams may fit the practice squad.
With a premium on roster spots a versatile veteran that can fill two positions is better than either Rosario or Williams.
You also got to be able to catch if you're a TE too which Hartsock can't. If Williams keeps improving, Hartsock is on the bubble.