You can certainly have two different "curries" on the plate, including, say aloo gobi and a beef masala of some sort; but that's straight head Indo/Pak food.
If you're going to do sliced, roast beef, I agree with the other posters that you're better off not doing a "curry" sauce for the beef. A simple jus made of stock, red wine, Worcestershire and a few aromatics, then reduced, strained, and dressed with herbs would be fine and would enhance rather than take away from your cauliflower.
A horseradish cream made with horseradish, a touch of strong mustard, brined green peppercorns, a little minced parsley, all mixed into creme-fraiche (or sour cream) and mayonnaise -- is always good with beef. Served on the side it won't war with cauliflower.
You can, if you like, sauce the beef with the jus, AND pass a horseradish cream.
In my experience "curry powder" is flat and stale compared to a freshly ground masala made from whole seeds and fresh ingredients, but as long as you choose a good powder and make sure to cook the raw off of it with the onions and ghee, before adding the rest of the ingredients it's OK. In fact, some pre-mixed powders are very good; anyway most cooks commit worse sins against their dishes than using slightly stale spices.