Barring going after the rare Julio Jones, Larry Fitzgerald guy that comes along every few years, the 1st round is not the best place to get WRs usually. It's not that 1st round guys don't become OK NFL WRs, it's that often they don't, and more often than not they become just average WRs. So the price is too high and the value isn't good to go after the rather typical 1st round college WRs that come out every year. There IS no special WR this year and none worth a 1st rounder in my book.....and that includes Riddley. Second round? Yes.
I really doubt the Rams would spend their 1st round pick on a WR.
I see OLB most likely; LT next most likely; and then TE.