Rollei film is a brand from Maco. They have three manufacturers:
Agfa Gevaert for the Retro S films and IR incl. the ATP1.1 micro film. Filmotec for the Ortho films. And Harman Ilford for their RPX film line. All these films can be bought in bulk, even the C41 and E6 Rollei Digibase CN and CR color films (also from Agfa Gevaert).
The prices in Europe for these products are pretty good. If you want real cheap and reasonable quality film you can look at OrWO Filmotec UN54 and N74+ In 122m/400ft. Alternative TSF type film but then the quality sucks.
When going to Foma: Also good film but their Fomapan 400 is only iso 250, FP200 iso 160 but a very nice film in structure, grain but soft in emulsion. FP 100 a classical iso 100 film. All available in bulk for a reasonable price.