How to roast a 9 pound sirloin roast?

I am a beginner cook. They have these big Sirloin Tip roasts all the time at Smart and Final for cheap. I bought one, and the young guy who worked there just said cover it with seasoning (rub, S&P, whatever) wrap in heavy foil, place on cookie sheet and roast at 275 for 5 hours. He says that's how restaurants do it all the time. My husband, who is more picky about cooking, said I need to "research" it. He is afraid I will not do enough (just boil it), and I am afraid he will do too much (make something super fussy and mess up the whole kitchen and it still might not come out right).

I like the idea of seasoning it, wrapping it in foil and sticking it in the oven. That sounds like something I can manage. But I can't find anywhere what degree and how long is correct. Is 275 too hot and is 5 hours too long? I don't want it dried out, bland and gray. They have these roasts there all the time, so if I can get it right, that would be an easy repeat meal that could provide leftovers for days.

Thanks for your help. :)