We stayed there last year. I do not remember seeing a microwave there. That doesn't mean they don't have one. Perhaps someone else knows for sure. I know someone who brought their own microwave with them. You could do that if you are driving. Not so easy to pull off if you are flying.
Just to follow up, I got curious and checked to see what I could find. I read that the food court does have microwaves available. That's what I read anyway.
Go to the Disney World website. Click on "Things to do". Click on "All Dining". Look for "Riverside Mill". Click on riverside mill and than there will be a menu icon that you can click to see the menu. Select breakfast, lunch, or dinner.
Almost all disney resort food courts have a microwave. "almost" all.....not sure which ones dont. But i've been to every value and moderate resort and they've all had them.