Slightly bent? How slightly? Sometimes, you can remove the pressure plate and push it back with your thumb.
As long as the pressure plate does its job, then it should be OK. You want to make sure that the back closes tightly so that no light can enter the film chamber.
If you can post a photo, some folks here probably can offer some better advice.
I've had a couple of Rolleiflexes with depressions in the back door that I was able to push out with my thumb.
It is definitely not like twisted. I believe a slight bend may be in between 0.25-0.35mm which makes closing and opening the door a little hard.
* I lay the door on flat ground and pulled a little towards me and now it seems very smooth in closing and opening. I will test a roll and see how it goes.
Previous owner might have used on tripod without Rolleifix...
It should be fine. Those backs are so thin and malleable it's easy to tweak it straight w/ just your fingers. But as you said, shoot a roll to see how it goes. The springiness of the pressure plate will make up for a lot of things.