The Valencia club parted with Roneeka Hodges in December but added Wiggins, who was a college standout at Stanford University before representing the United States at the 2008 Beijing Basketball Test Event and then playing in the WNBA with the Minnesota Lynx.
"I am delighted to be in Valencia," Wiggins said.
"I am looking forward to playing. Ros Casares is an incredible club and I feel ready to help them. The play is slightly different, especially in terms of rhythm, but I think I will be able to enjoy myself a lot playing with DeLisha Milton-Jones, Amaya Valdemoro,, Elisa Aguilar and Laia Palau."
Ros, who like to play an up-tempo style of game, finished second in EuroLeague Women Group C behind UMMC Ekaterinburg and will face Maxima Broker Kosice in the Eighth-Finals Play-offs.
Wiggins who averaged 15.7 points per game in her rookie campaign with the Lynx, doesn't turn 22 until next month.
"I consider myself a leader but I know that this is a special team," Wiggins said. "I know my role will change."