I was just about to try to raise it up and noticed that the surface roots are completely white and somewhat thick if this helps any.

Rhododendron roots are very fine and hair-like. The thick white roots you're seeing are almost certainly from the tree. They have made their way into the moist peaty area over time and are taking up all the available water and nutrients. This is causing the rhododendron to wilt because it is simply unable to get enough water. The first and last photos do show some reasonably healthy green leaves on the rhododendron, so the rhododendron root system has not rotted away. A few of the middle photos - the second one from the top especially - do show branches that look extremely desiccated. Branch dieback is fairly common in rhododendrons, especially in those experiencing stress from too little or too much water. There's no way to tell from a photograph if this is the case or if it is just from extreme dryness.

Best thing you can do is dig up the rhododendron, soak the root ball in water for 30 minutes or so and replant. (Should the rhododendron roots appear moist when you dig them up, then I'm wrong and you probably do have some sort of fungal infection preventing water uptake. I'm betting, however, that they will be dust dry and entangled with lots of tree roots.) Growing rhododendrons in the shade of trees, especially maples and other species with aggressive roots, is a challenge. Avoid peat which becomes very hard to rewet when it dries and use bark instead. Water the rhododendron with just a trickle from a hose at its base. You can try cutting around the rhododendron with a sharp spade two or three times a year to sever the tree roots but this is never very successful in my experience. Once the rhododendron has grown a larger root mass, it can compete with the tree roots, but until then it will need a lot of TLC. There is a very well done discussion of growing rhododendrons under trees at the Singing Tree Gardens website if you're interested.

This is extremely helpful so I thank you! I could have sworn the white roots were from the Rhododendron because when I say thick I don't mean finger sized thick or thicker. They were very hair-like, but for hair it was pretty thick. Kinda like dreads but a little bit less thick if you can picture that. However I think it would confirm the problem just by digging it up and checking the roots like you said so thanks for the advice again!
I'll look into all of this.

Edit:

They were tree roots. I understand now. There weren't a lot because it hasn't been planted for very long, but they were tangled into the Rhodo, too. And when I brought it up it wasn't BONE dry, but it was mostly dry. It FELT moist, but it wasn't really. I'm also gonna try to raise it a little better because I think I had it too low last time. As for mulch...I'm sure the playground won't miss a little bit of it. ;)