From Longman Dictionary of Contemporary Englishroller skateˈroller skate noun [countable] 
DLa special boot with four wheels fixed under it, used for skating on hard surfaces → Rollerblade, in-line skate —roller-skate verb [intransitive] —roller skating noun [uncountable]
DLa special boot with four wheels fixed under it, used for skating on hard surfaces → Rollerblade, in-line skate —roller-skate verb [intransitive] —roller skating noun [uncountable]Examples from the Corpus
roller skate• All we do is dance and roller skate. 