Johann, the amount of pictures you need to shoot does NOT depend on the head/rotator device. The head/rotator only makes it easy to align to images properly. With a Samyang 8mm f3.5 you'll need 4 pictures around and 1 up and optional 1 down if you want to patch the nadir/tripod. I personally use NodalNinja3MKII+RD8 rotator, but that's just what I use, and what I'm happy with. I don't know enough about heads and rotators to recommend that it's the best or if there are any better alternatives. You can even use no head and no rotator and no tripod at all if you know how to align the images properly while taking the images handheld. The easiest in that case is a string attached to the nodal point of the lens with a weight touching ground that makes you sure you keep the camera in the same distance from the ground and at the same spot.

The 4+1 is a nice approach that i was using, but it has a problem, if there is no texture in the "up" image then there would problems doing the stitching, and in every case you don't get good image coverage except in the floor. What i am doing is getting 8 images, 4 with -15 pitch degrees at 0, 90, 180, 270, and 4 with + 15 degrees pitch in 45, 135, 225, 315.