The most important thing you can do is start out with the right plane. This "patriot" doesn't sound like a very good plane, let alone a good beginner plane. Can you provide a link to where you got it from, and maybe some specifications? Maybe there's something that can be done to improve things without resorting to buying another plane.

Rolling over to the left and nose diving indicates that the plane is stalling. Pulling too much up elevator, or trying to climb too steeply will cause this. Remember, the elevator controls attitude. Throttle controls altitude. Keep the climbs gentle until you get a feel for what the plane can do. In fact, just fly level for a ways after launch to let the plane get up to flying speed first.