We don't even think about singular or plural any more when writing title tags.
Here is a suggestion. When you visit a news site and see the content promotion ads from Taboola, Outbrain and others, read their captions. Those captions are designed to elicit clicks often to the point of being spammy, suggestive, explicit or vulgar. The people who write those title tags are experts. They know how to get the clicks and getting the clicks, I believe, is a huge ranking factor in the organic SERPs.
I have learned a lot from them and although I really dislike a lot of their ads they can give you an education. So, if I was selling foam rollers, I might consider title tags like...
Foam Rollers - Get yo' bones straight
Foam Rollers for when you back is out of whack !
Those are just very quick efforts and you can certainly do better because you know the product and how people use it. If there was a lot of money to be made selling foam rollers I would be spending a LOT of time to get a great title tag that makes people want to click into your webpage.