Not meaning to come off as a draft guru, because we have some really good ones on this board.
But as I look back from my armchair, it's the 3rd and 4th rounds where drafts are made. Lots of 2nd year starters to be had there.
Long term stats say it's not that hard to hit on your 1st rounder. Same stats show a big reduction, 2nd round a little harder, but you're still dealing with the top 50 or so players coming out so lots of rookie year starters.
It's the 3rd and 4th round where a GM can make hay. Get some guys that are overlooked, or maybe had a medical (like Terrell Lewis), or perhaps are really good players at smaller schools, or have all the physical and mental attributes but need a little more seasoning and coaching-up (development).
The Pats showed the way on this, and Snead was smart to spot it. That's why it is absolutely brilliant to keep bringing in young guys as FAs who were drafted high but have under performed, sign them for a year, plug a hole, and then if they do great (Fowler and now Floyd), should they leave you get a 3rd round comp pick which turns into some really good players on the cheap.
And yes, it's not that every round doesn't present opportunity. But those 3rd and 4th rounders can become some really good players and the Rams recent drafts prove that. In fact, that's where Snead excels. And he tries to stock up on them, while other teams see them as ways to move up in the top 2 rounds (not that there couldn't be a good reason to do that).
Even if the Rams decide they have to move on from Goff (and I don't think that is at all decided) in a year they'll have good ammo to do that.