Murphy died Sunday at age 32. The circumstances of her death are still under investigation.
Murphy and Roberts appeared together in "Spun," and will be seen next year sharing the big screen a second time in "The Expendables."
"I would like to this time to offer my sincere condolences, deepest sympathy and prayers to the family of Brittany Murphy," Roberts said in a statement Tuesday. "I am saddened by her passing. She was a terrific young lady and an incredible actress. It was a genuine pleasure to have worked with such a talented individual. Brittany will be greatly missed by her family, friends and fans. Her untimely passing is a tremendous loss for Hollywood."