Spinach, artichokes or arugula would be a great in addition to my salad. I didn't suggest anything other than the cheese ravioli or tortellini because the OP wanted a vegetarian dish but there are many many wonderful meats, chicken or seafood filled pasta's as well as veggie. I would think a spinach, mushroom or pumpkin/squash filled pasta would work quite well.

I would also refrigerate the pasta salad for a while, and then let the pasta salad come to room temp to let the flavors develop. If the oil solidifies bringing it to room temp will fix that.