Rousey (5-0) is a former Olympic judo bronze medallist known for her armbar finishes in MMA.
"She's submitted all of her opponents thus far, but No. 1 contender Sarah Kaufman has the experience and tenacity to push her like no one else," Strikeforce CEO Scott Coker said in a statement.
Rousey won the 135-pound title by defeating Miesha Tate in a March bout that Kaufman (15-1) thought she should have been part of.
The 26-year-old Kaufman lost her title to Marloes Coenen by third-round submission in October 2010. She has won three straight since.
The card will take place at the Valley View Casino Center.