Roller bar with the bearing

Print with 0.2 layer height with random seam position, NO support. Printing time with K1 Max 2:40h

Open the roller, loose the top cap (with the knife). 
Outer shell & bearing needles should be free so take them out.

Bearing needle guides are probably welded a bit on the caps. You can remove them carefully (& turn upside down to get smooth surface towards the end caps) to get extra smooth rolling.

Assembly the roller:
-Bottom cap with core
-Bearing pin guide on the bottom
-Outer shell
-Place the needles around the core, see that they ends go in to the guide's holes (all pins at the same level)
-Upper pin guide
-Upper end cap. (You can use a drop of super glue secure it)

Now you should have reasonable free rolling filament holder bar :-)