From the Skullgirls mobile Wikia:
"Starlight Rose can provide ENRAGE and REGEN with BARRIER from all sources. This means that variants that can grant BARRIER (especially timeless BARRIER) such as Corrosive Agent, Snake Bite, Feathered Edges and Overclocked can benefit from having her in the bench to provide a boost in damage and sustain, which is particularly useful in Rift Battles."
No idea why they didn't mention Rock Star, but she also provides barrier when tagging in while she's alive, as well as Maid Of Honor which grants barrier when parrying a hit.