Tri-Slosher and Slosher have great support specials so I would definitely run special charge up. Ink resistance and bomb defense up are great if you plan on jumping right into the fray.
Carbon Roller is interesting because it is usually a sharking weapon but has a decent support special in Splatoon 2. I would use swim speed up, bomb defense up, and ink resistance. If you would rather play a support role more then a hyper offensive roll with the carbon, I would run swim speed up, special charge up, and bomb defense up. If you use the autobomb an aweful lot, go with ink saver sub.
Sorry for the lack of other abilities. The ones I listed are just that good and are used through the entire match.