By Roblox hair do you mean any hair accessory on Roblox or a hair made by Roblox?
Are you sure it was all one item as you described or could it have been multiple items? (Did you go to the catalog page at one point and see it was all together like that?)
Do you know when you saw it? Even a year helps narrow down the timeframe by excluding items made after then.
You could also try to make a rough sketch of it in a paint program to post here - even if it’s not amazing, having a visual reference can help narrow things down and clarify the description
