In Japan, she trained at the Cross Point club in Kichijouji, which taught both Muay Thai and BJJ. She hopes to one day write a book about her experiences during that time, having already contributed several articles on the topic. After graduating in May 2005, she secured a position with Berlitz, teaching English in Japan and arriving for the second time in July 2005. Modafferi earned a win by split decision against Cassandra Rivers-Blasso at Fatal Femmes Fighting on February 2, 2007. She became K-GRACE Women's Open-Weight Tournament Champion by defeating Hee Jin Lee, Megumi Yabushita and Marloes Coenen on May 27, 2007. Roxanne defended her FFF title against Vanessa Porto at FFF 4 – Call of the Wild on April 3, 2008. She won the fight by TKO in the third round. She signed a contract with the American Fight League (AFL) and was scheduled to face Tara LaRosa at the AFL's November event, but fought instead at the debut Valkyrie event in Japan after the AFL's plans stalled. Modafferi moved up a weight class and made her long-awaited Strikeforce debut in a rematch with Marloes Coenen at on November 7, 2009, but lost the fight by armbar in the first round. On January 30, 2010, Modafferi submitted Molly Helsel in the second round at in Okinawa, Japan. Modafferi rematched Tara LaRosa at Moosin: God of Martial Arts on May 21, 2010. Strikeforce provided official permission for Modafferi to compete on the card. Modafferi won the fight by split decision. Modafferi returned to Strikeforce to challenge Sarah Kaufman at Strikeforce Challengers: del Rosario vs. Mahe on July 23, 2010. She lost the fight via knockout due to a slam in the third round. Modafferi was released by Strikeforce on November 12, 2010, after losing both her fights with the promotion. She was scheduled to face Hitomi Akano at World Victory Road Presents: Soul of Fight on December 30, 2010, but the fight was cancelled after Modafferi suffered a stomach illness and was unable to compete. Modafferi faced Rosi Sexton at Cage Warriors Fighting Championship 40 on February 26, 2011. The fight was Modafferi's debut at 125 pounds. She was defeated by unanimous decision. Modafferi then faced Hitomi Akano in a bout rescheduled for Jewels 15th Ring on July 9, 2011.