When pressure cooking a pot roast, it is best to check the manual and recipes that came with your pressure cooker. This is a Tried And True recipe from the Cook's Essentials 8-quart Electric Pressure Cooker manual. (If you have a 15 psi pressure cooker, like Kuhn Rikon, the pressure cooking time would be 60 minutes, per "Quick Cuisine.") Note that a 5-liter pressure cooker can handle up to a 4-pound roast, and a 2-liter p.c. can handle up to a 2-pound roast. I always keep a can of condensed French onion soup in my pantry for emergencies. Cooking time includes 15 minutes to reach pressure and 15 minutes to reduce pressure, and 80 minutes at pressure for Cook's Essentials pressure cooker.