The terms "rice cooker" and "rice steamer" are synonymous. The American version of rice cookers come with an optional pot to steam vegetables above the rice where the heat rises from.
A product on Sears's online store uses both "cooker" and "steamer" in the name. The Zojirushi rice cooker is an excellent example of a Japanese rice cooker company that manufactures products that only cook rice.
The Aroma 8-Cup Digital Rice Cooker and Food Steamer is sold on an American online retailer and contains an additional pot as an accessory. The pot is left inside on top of the rice, while the cooker operates, and vegetables and meals can be steamed at the same time.