Ashley, rather than roast, could you grill, pan-fry or broil smaller cuts?
It only takes a few minutes to do up a steak.

And rather than mince, you could do up stir-frys with meat and veg - even
cut the meat/veg beforehand so all you have to do is remove them from the
fridge/defrost and pop them in the pan. Even chicken cooks up fast this way.
You could also do up a bunch of mince at once, portion it out and freeze it.
It does keep in the fridge as well.

I can see how things take a long time if you're doing all the prep at the
same time - could you spread your prep work out, or do it all at once for
the week? Cut veggies/meat and vacuum bags are good friends. Even just in a
zipper bag for the week would be fine.

Crock pots make doing up larger meat cuts easier, and are a cinch to use.
Making stews, chilis, soups etc is easy - add ingredients and walk away.
Then you have leftovers!

BTW,  if you're eating once a day, you're already doing IF.

Tracy