This is a straightforward design that incorporates emmetts parametric gear bearing. 

The roller uses 0.2mm tolerances, and has a larger hole carved out the center to use a thicker/stronger peg to hold it up. I was able to print it easily at 0.3mm layer height, and a 0.6mm nozzle.

The base should be printed with strength in mind. Thick walls is a must, for the long cylindrical section to be strong. Infill on the base probably doesn't need to be 100%, but again, you want to make sure it's sturdy. The peg/cylinder part of the base is slightly angled upwards, to counteract the inevitable sagging caused by tolerances and malleable materials, so make sure you pay attention to which way is up (up has two screw holes). 

In my testing, the roller fits decently snug on the base. Then, I just use the peg.stl with a dab of glue on the end to firmly fix everything together. If you'd rather avoid glue, the peg prints quickly, and could be sized up very slightly to get a stronger friction fit. 
 

I printed mine with Polymaker PLA. I tried snapping one of my earlier test models, and It was pretty strong, so I don't think strength will be a concern unless you print it really thin, or have layer adhesion problems.