Elk Roast

Cooked an elk roast for the first time tonight...cooked it in the oven in a magnalite pot, which is how I usually do beef & pork roasts. Damn thing came out tough and dry...not quite shoe leather, but definitely nothing I'd want to serve anyone. I browned the roast on the stove and then put it in the oven at 350 for about 2.5 hours. Did it with the carrots, onions, garlic, gravy...in fact that was the only part that came out good.

Any suggestions on how to keep an elk roast tender and from drying out? Was I wrong on temp., time, or both? For the record I don't have a crockpot...would prefer to use the magnalite or my cast iron pot.