Candice Patton (likely best known for her appearance on The Game) has joined Jesse L. Martin in The CW’s Flash pilot, which stars Grant Gustin as Barry Allen aka The Flash, the title character. 

Patton has signed up to play Iris West, daughter of Detective West (Jesse L. Martin’s character), a respectable, blue-collar cop and surrogate father to Barry Allen/The Flash. Iris West is also Allen’s best friend.

Based on my research, in the comics, the character West is white, and is the father of Barry’s/The Flash’s eventual wife, Iris West, who is also white.
But character breakdowns for both Detective West and Iris West, which circulated the web last month, indicate that they will be African American (obviously, based on this casting), and give us a bit more background on each:

IRIS – 22-28 – African American – As smart as she is beautiful, Iris is in grad school studying psychology. She’s also Barry’s mile a minute, fast-talking, quick-witted best friend. Her father, Detective West, took in Barry when his mother was murdered, and his father was wrongly accused and imprisoned for her murder. In a tough childhood for Barry, she was the one “not tough” thing. She’s unaware of Barry’s strong feelings for her. 
DETECTIVE WEST – Late 40s to Early 50s – African American – Detective West is an honest, blue-collar cop who’s seen it all. A soulful, funny caring father to Iris, and a surrogate father to Barry, West came up through the foster system himself. He took in Barry after his mother’s murder and his father’s imprisonment. He believes in Barry and supports Barry’s efforts to prove his father’s innocence.
I believe that a romance also springs between Iris and Barry in the comics. Those in-the-know can verify that.
I’m sure this casting “race-change” news will attract the usual onslaught of racist comments. 
The show is actually a spin-off of The Arrow, and will be executive-produced by Arrow executive producers Andrew Kreisberg and Greg Berlanti, as well as DC Comics’ Geoff Johns
In addition to The Game, Patton also saw stints on Entourage, The Young and the Restless, and Heroes.