What set do these large grey circular pieces belong to? (possibly a Star Wars set) I got these pieces in a bag full of random pieces.
The decorated 10x10 dish is easy, it has only been in 7748

Those round corners aren't in that set. In light bluish gray (that you have one of in the picture), it has been 5 sets, in dark bluish gray (that you have three of in the picture) it has been in 4 sets, there are no sets that have contained that piece in both colors. You can find the list of those sets on bricklink by following a few links from the linked page about the part.

The conclusion is that there are parts from at least 3 different sets in that picture.