Procyclery on W Sahara. Rented from there 2017 I think it was, and whole experience was awesome. I got a wilier with mechanical DA9100 and wife had Scott solace with ultegra. Close to outskirts easy access to red Rock canyon loop. Staff super helpful and a great shop and location.
I just rented some bikes in Vegas last weekend and went over to Red Rock Canyon (which was great btw).
I don't have a company that I specifically recommend, but I can say from my experience that I do not recommend Bike Blast. The delivery and drop off was a huge pain and poorly set up, the bikes were VERY poorly maintained and not in good condition, and the customer service was poor (including having us follow their guys all the way to their warehouse because of a bike error their mechanic made).
2nd for Pro Cyclery at 9440 W. Sahara Ave. New Argon 18 Krypton carbon road bikes, Ultegra 8000 groupset, and disc brakes. Very well maintained and close to Red Rock.