If the bb feels rough the bearing surfaces are almost certainly trashed. It's acceptable to use loose balls to improve a headset, but not a bb.
A high quality, compatible cartridge unit is relatively cheap.
It's a no brainer.
Cartridge units also massively extend the time between bb services, and each pressfit install/removal of a square taper crank damages the taper, so it's good for crank life.

UN-55 is the recently discontinued high quality shimano unit to look for as old stock, lots of bike shops still have em, the replacement un300 is good but not as good.
If you have an asymetric spindle, get a 73mm bb (your frame is almost certainly 68mm as are most bottom brackets), and use 5mm of spacers to mimick the asymetry.