If you don't have the welding equipment to make the frame tie-ins, any off-road shop that makes roll cages should be able to help you out.
A full on roll cage where the seats tie-in and the cage is tied to the frame is the absolute best solution. However, custom cages are expensive. I guess the need all depends on how you use the vehicle and how much you like your head.
Here you can see where some of mine go from the frame rail/tubing up to the body. At the body you have sandwich plates on the bottom and top. Your roll bar foot would be the top plate.
You can also see a glimpse of the seat cage.