I've found the b&q rollers to be fine for applying west system & sp epoxy, both for coating and glueing. Lifetime is around 10 minutes, the solid foam end normally has to be torn off after about 2! Doesn't work out much cheaper than using the west brand ones unless you buy loads (I think i've got boxes of 12 hamilton? brand). For solvent based material you need to use yellow foam ones, eg West, white foam start ballooning & detach from spindle after a minute.
Coppercoat supply & recommend mohair rollers, but that has a completely different consistency & is water based I believe. I also got these & yellow 9" foam rollers from my local SDM decorators merchant (London only?)
Epoxy application is used for high strength or better water resistance in most cases, using rollers prone to falling apart can destroy the strength and the resistance to water ingress. A single bristle or hair can allow water or chemical penetration as can a small lump of foam.
If you purchase the correct roller you will be able to clean it and re use it many many times, in fact an older roller works better than a new one in many cases.
You can remove most of the uncured epoxy resin from a roller or brush with bog standard white vinegar, then finish with acetone, this means you use less acetone and if you stand used acetone in a clean jar, the sediment will settle out and you can re use the clean top layer over and over again.
Why someone would risk contaminating an expensive epoxy resin is beyond belief.
Tip:
Epoxy and cloth (Not chopped strand mat) should be applied at a 1 to 1 ratio of resin and cloth by weight.
Standard resins need a 3 to 1 ratio by weight, 3 resin to one CSM.
An expert of my acquaintance doesn't use rollers, he pours the stuff on then works it in with a bit of flexible plastic sheet. It seems to do the job as my mast hasn't fallen down yet.
Yes using a squeegee or plastic sheet like credit card material is fine on the flat or an item you can rotate, also leaves a smother surface finish, also good with standard resins, if you can time it just right you get a super smooth finish on flat surfaces.
We use them when waterproofing floors that will have vinyl over the top, as it must be very smooth and flat. The can be used on rounded surfaces provided the curve is in one direction only.