There is no greater gamble than drafting a QB high.
And, as for this supposed new type of NFL QB that has to be a great athlete who can run, I don't buy it. It's when those great athlete QBs learn how to stay in the pocket and pass the ball that their team can be really good, and the QB can stay healthy.
That doesn't mean that a modern NFL QB shouldn't be mobile in the pocket and able to improvise out of system ala Aaron Rogers. But that isn't the same thing as a great athlete who runs well, because that's what they'll do; most of them will not survive in the NFL.
Even so, the Rams shouldn't be drafting a QB higher than round 2, and they should draft a potential starter every year until they hit on one. In the meantime, nurse Stafford along, and see if they can resurrect Wentz. They'll win more games than any rookie QB will.