Rosemary will go just fine with those ingredients if you don't have thyme.

Try onion bhaji ( spicy Indian snack of which the main ingredient is onions )
http://www.hub-uk.com/foodpages12/recip0590.htm

I love roasted red onions - sometimes with other veggies, but can do without as well. Just olive oil, salt and pepper. Rosemary is good too. Cut them in nice big chunks.

I think the balsamic, honey and butter idea is up my ally, but I don't have any thyme--rosemary OK?

French Onion Soup, Pickled Red Onions, and caramelize them and stick them in a jar.

Have you ever made musakhan? It's a Middle Eastern dish of roasted chicken, bread, and tons of red onions! I always make at least 1 1/2 times the amount of onions called for in the recipe b/c it seems to be everyone's favorite part. Even if you don't have all the spices (sumac can be hard to find) it's still delicious. Comforting, too, for the fall! Here's a recipe similar to my mother-in-law's: http://www.channel4.com/food/recipes/popular-ingredients/chicken/musakhan-recipe-08-03-19_p_1.html

Absolutely, caramelize them! Slice as many as your slow cooker will hold. Toss in the slow cooker on low with some salt and a stick of butter. Turn on low and forget it for 18 hours (except for the gorgeous smell that will permeate your house). When they're done, cool and package in plastic baggies and freeze; I like to put mine in one-cup portions.

pickled red onions are great on sandwiches and tacos - there is a link to a recipe here - http://www.folksgottaeat.com/2010/09/because-you-can.shtml - they turned the most gorgeous hot pink and were great for hostess gifts last Christmas. I did about 8lbs of a ten pound bag - the rest we used roasted and we made caramelized onion tartlets.

Another thing you can do is pickle some of them, pretty thinly sliced, to keep as an element to add to sandwiches.

I like to whisk together honey, balsamic or sherry vinegar, thyme leaves, and a little hot water. Then I cut the onions in halves or quarters, depending on the size, toss in the glaze, and season with a little salt and pepper. Then they're ready to be roasted until tender and served alongside whatever your main dish happens to be.

Condensed onions (cooked and caramelized forever, then put in jars, to can for shelf stability or otherwise, refrigerate) or red onion marmalade. If you need recipes, please contact me. I can't post them due to copyright restrictions but can share under fair use, one-to-one. ;o)