Per wiki policy, Spoilers Off applies here and all spoilers are unmarked. You Have Been Warned.
Roxanne "Rocky" Ballantine's revolutionary new metal alloy was the foundation of Batman's new suit in Batman Beyond.
See the Batman Beyond Wild Mass Guessing section for more details. Bruce Wayne hinted at this when Roxanne told him she didn't know how the metal could be made useful, telling her he had a "silent partner" who might be interested, and he certainly had the means and motive to pay her off, destroy all records of her, and quash any investigation into her work history in return for exclusive use of her alloy.
