What I do with the roasts is to keep the best ones - sirloin tip, rump; ask for some rolled roasts but have the processor grind most of the arm and chuck roasts, etc. They are much more useful and make good burger rather than leaving them as roasts.  I have also started keeping the oxtail. Also ask for some flank steak which is used in many Mexican recipes. It is surprising how little flank steak you will get out of a steer, however.

If this is a good, finished steer (not an old cow) I would not specify any given fat to lean ratio on the burger. That is a supermarket thing where they blend fat in.  If you have a good processor and good carcass, just let the grind be what it is. That will produce the best burger, not adding trim fat. I find 1 lb burger packs are too small for many meals, 2 lb is too large, so get all burger in 1-1/2 lb packages.

On the round, you can either take it as is, tenderized once into cube steak, tenderized twice into Swiss steak or have most of it ground. I take some as Swiss steak and grind the rest. There is usually a lot of round and it is more useful as good ground beef.

I also specify for everything to do a lean trim and minimum bone. I do ask for soup bones but mostly for the marrow and soup, not with a lot of meat on them. Some processors leave soup bones looking like steaks. That meat along the bone is tasty and best used in good ground beef.

Doing a good job of processing takes time and experience. Choose a good processor. It is an art.

Good luck.

edit to add: I agree with Hereford Guy's comments on stew meat. Very useful. However some processors don't like to do stew meat as it takes a lot of time and care to do a good job on it.