WordNet records no synonym and no antonym for roll-on. It is the only member of each of its synsets, which is common for technical, taxonomic and single-sense vocabulary — there is no other English word that means the same thing. The broader and narrower terms below are the useful relations in that case.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a dispenser of a liquid cosmetic (such as a deodorant) having a revolving ball as an applicator
a woman's foundation garment rolled on to the hips
Synonyms, antonyms and the broader and narrower relations for roll-on come from Princeton University’s WordNet. Full sources and licences.