According to
Bloody Disgusting, they we're exclusively told that Michelle Rodriguez has signed to reprise her role as "Rain Ocampo" in
Resident Evil: Retribution.
The character was first seen in the first movie back in 2002, she was eventually turned into a zombie and killed by the character Matt in the process.
Also according to the site:
We've also learned that Shawn Roberts' return as Albert Wesker will be in the form of a cameo.
Resident Evil: Retribution has now on the cast Milla Jovovich, Sienna Guillory, Boris Kodjoe, Shawn Roberts, Michelle Rodriguez and Colin Salmon confirmed and is set to come in September 14, 2012 in 3D!