Muscle Roller

To print the outer part use TPU 92-95A I would use specific settings, including: increasing the wipe by a lot (12mm), constant speed for everything at 20-30mm/s, and as fast travel speed as the printer can. 
I would also use a 10% cubic infill depending on how firm you want your roller to be, 2 perimeter walls, and 3 top and bottom shell layers. And I would suggest putting Ensure Vertical Thickness to Critical Only.
I would recommend a bigger nozzle (0.6-0.8), as there was still a little dropping on some of the overhang with the 0.4 nozzle, but not enough to affect the print.

For the inner part I would use PLA or PETG, using 3/4 perimeter walls, and 25% 3D honeycomb infill.

And of course especially made for NO SUPPORTS needed

Best of luck with the print!

From the first model, I changed from the original design the scale, so that it can print better with less steep overhangs. And also changed the design for it to be more symmetrical, and easier to print. From the second model, I copied the inner cylinder idea giving the roller the ability to keep it's shape during use.