Staite has been cast as Rachel Turner, described as "a tech genius/roboticist who exists in a future in which technology has an even firmer grip on our lives than it does today." She'll appear in episode 10 of the series.
They go on to describe her as one of a "long line of inventors," with someone from the DC Universe in that line. The only prominent "Turner" in the DC Universe is Ben, aka Bronze Tiger, who has already appeared on the in-universe Arrow series. Of course, her last name doesn't necessarily hold the clue. We've seen, or had a few hinted at, some other inventors in Arrow and The Flash, though. Ted Kord has been consistently hinted at on the shows, and of course characters like Ray Palmer, Cisco Ramon, and Curtis Holt are no slouches in the inventing departments, themselves.
When some of her tech is destined to fall into Vandal Savage's hands (and be used for nefarious needs), Rachel has to team up with the Legends team to stop his mission.