If you’re looking for something special in the slow cooker, by all means add onion, garlic, beef stock, herbs and a liberal dash of red wine. Check out this easy to follow recipe if using the slow cooker:
https://www.greenmeadowsbeef.co.nz/Blog/August-2016/Slow-cooked-Rump-Roast
Or, try the Rump on the BBQ during summer. Sear and then turn the temperature down until the roast is cooked to your desired ‘done-ness’. With a layer of fat on the outside, ensure this is well caramelised before serving.