I'd like to see the Rams take a WR in round 2 or 3 to play the WR3 role next season, in hopes that in another year or two, he can grow to be a strong WR2 behind Puka when Kupp might be more of a WR3.
I don't think Robinson will be affordable for the WR3 role. If he is, bring him back. But I doubt he will be. And on that note, I don't think free agency is the answer vs. the draft. You usually have to overpay a bit in free agency. Who wants to overpay for a third WR? There are better places to throw money, where the Rams also happen to have bigger needs See: pass rusher. Take the rookie with the several years of a cheap contract.
Another option is to pay for a stud in free agency and completely load the position. But that is risky. WRs are divas. Rams WRs have to be humble. They have to be okay blocking, and on any given night, whatever stud WR we bring in would have to be okay playing 3rd fiddle to Puka or Kupp. Perhaps even 4th fiddle if the run game is going. How many studs would accept that? Probably none that are not already on the roster.
If we are going the vet route for WR3, I'd forego free agency and love to get Adam Thielen via trade if we could somehow pry him out of Carolina, if his contract is not too expensive? He looked to have lots left in the tank this year for Carolina. He'd be great for the role I've described above. Bonus that he is an absolute monster in the red zone. Rams sure need help there. Especially as McVay seems to always want to throw it and not run it near the goal line. Panthers might accept a pick for him as they are rebuilding, but for the same reasons, might want to keep his veteran presence around for the youngsters.