You're allowed not to know! It's just that since you'd got Picard I thought you'd know the rest since they're from the same show (Star Trek: The Next Generation).
Seeing as I've just discovered you can use tables on Lemmy, I'll give you a proper answer:
| Actor | Character |
|---|---|
| Patrick Stewart | Jean-Luc Picard |
| Jonathan Frakes | William Riker |
| Brent Spiner | Data |
| Gates McFadden | Beverly Crusher |
| Marina Sirtis | Deanna Troi |
| LeVar Burton | Geordi La Forge |
| Michael Dorn | Worf |
| Denise Crosby | Tasha Yar |
| Wil Wheaton | Wesley Crusher |
| Colm Meaney | Miles O'Brien |
| Diana Muldaur | Katherine Pulaski |
| Dwight Schultz | Reginald Barclay |
| Michelle Forbes | Ro Laren |
| Majel Barrett | Lwaxana Troi |
| Brian Bonsall | Alexander Rozhenko |