First thing I'd check is the rear pads, the CR-Z chews up rear pads faster than the fronts due to the regenerative braking and you can hit the wear bars pretty quickly. Its quick and easy. While you're there check what Litz suggested for proper caliper function.
Second, your noise description does sound accurate to a rear bearing but if you can't feel play or any grinding/abnormalities while pushing and spinning the wheel yet or aren't positive I'd say keep driving. If it is the bearing it will get worse and you'll have confirmation and will also be able to feel the roughness while spinning by hand or side to side play, or both.
Also on those bearing replacements you listed does it come with the hub? The rear bearing hub assembly on the CR-Z is a slide/bolt on, the bearing is pressed onto the hub so you'd need to separate the parts if its just a bearing for those options just so you're aware. The Genuine Honda replacement comes as bearing and hub together.