Well if you want to cook mutton right then don't just roast it with potatoes in the oven. Make a nice pilaf with it, with a whole head of garlic in the center like they do in Uzbekistan:

https://youtu.be/tkCeL6Md0fg?si=q86eBrLRbJBJU4yi

Or stuff the leg with rice, as they do on the Greek island of Imvros:

https://www.youtube.com/watch?v=ZFVLLIZsh8A&list=PLsmrGn_1E1...

(the meat in the video is goat, not mutton, but it's the same recipe).

Or, my favourite (and a recipe handed down by my grandfather, though it skipped a generation): Gioulbasi, a whole leg of mutton wrapped in wax paper, with vegetables and melty cheese, and roasted slow and sweet:

https://youtu.be/OZjAiqC3ws0?si=93pwB2DZDNBtgNyF&t=6

Though these days I prefer to be all posh and use a French oven to slow-roast mutton (and lamb, and goat).