I lived in Vegas for a while, driving 4 different non-Interstate routes from there to Denver to see friends. So, take this comment/post for what it's worth.

It is possible.
You'll need to carry your own water/other liquids as the first 100 miles outside of Vegas have very iffy convenience store/refill/refueling locations. That is, they may or may not be open or in the locations you need them to be when you run out of water - which you will. I guarantee it. In Nevada, driving more than 10 miles anywhere during the summer risks over-heating (engine or person).

During my time in Vegas, I sold cars. (Key used car salesman jokes). We did do the "stupid asphalt parking lot tricks" to pass the time during the summer days/evenings- measuring the temperature of the asphalt in the shade, pouring water on the asphalt and watching it evaporate FAST in 105-117F heat (unofficial temps measured with different people's gauges), trying to fry an egg on a used car's hood (did it twice but took much longer than I thought it would), etc.

Shade, any shade wherever we could find it, was THE most sought after thing in the summer heat. And a 10-15mph breeze did little to make things bearable. I'm used to heat radiating up from the asphalt, but not like that.

Just standing around waiting for customers, I'd go through a minimum of 2 gallons of water daily.
You're going to be exercising - and NOT in the shade.

Will it be enjoyable?
Probably not. The heat is unbelievably oppressive and dry - as opposed to the humidity of the Deep South/Southeastern US. Both will drain you of fluids - just in different ways. In the Southwest, you'll sweat and get so little cooling effect that it'll be unnoticeable due to the high body temperature you still end up with; in the DS/SE USA, the humidity prevents the sweat from evaporating so no cooling effect at all.

That being said, yes, it IS possible to ride Vegas to Denver.
Your best chance of success/survival is to start before sunup, ride until 9 or 10am at most - the temps will probably be 95F or above by then. Then find a shady spot and camp/hide from the sun for the rest of the day. Keep in mind that temps above 95F are quite common even as late as 10PM in the Vegas area. Be prepared for the heat to NOT ABATE.

Be prepared to wear arm coolers/long sleeves and/or use up tubes of sunscreen - tubes, I said.

You'll want dark green sunglass lenses. As dark as you can find to protect from road glare.

A head covering (large brim hat/helmet, whatever) AND a neck covering is a necessity or you risk the worst sunburn you can imagine. Headache from sunburn on the head is not reducible via aspirin/Tylenol in my experience.

Do NOT drink alcohol while riding in the heat. It'll dehydrate you.

One other thing - SALT! You'll lose more salt than you think. Potato chips or other salt-laden foods are your friends, if you can stomach them in the heat. Some people can't.

Personally, I wouldn't do it as a solo in June, July or August - too much risk of heat stroke, heat exhaustion, heat prostration, and just plain unforeseen problems that end up stranding you in the heat on a low-traffic road for hours. With a companion for that just-in-case medical emergency, I might try it - if I were in my peak physical condition and I was still as bravely ignorant as I was in my 20s.