Sorry to take so long to reply - we just got back from a trip late last night. That looks similar to the pump I got. I've been so busy with my day job and other things, I never have made the time to work with the contraption as much as I wanted to. We just bought a home in the country that needs remodeled from top to bottom and we will be doing almost 100% of the work ourselves. My bees will need more time this year, but they will get less of it unfortunately this year.
The pump I got has four rollers and I think two is probably plenty. Use a quality clean power supply for your 24V DC and probably a 5K or maybe even a 1K potentiometer should work for your speed control, wired in series from the supply hot terminal to the pump. Make sure the product is listed as food grade - many foreign firms like to use lead in a lot of their plastic products.
email me if you want more details.
Hope this helps - Greg