If you’re going in the middle of the day when it’s not so busy, I’d say maybe 20 minutes because you can more or less walk on to the gondola without a wait, both at RIV and at CBR. At park opening times it will take longer because more people will be wanting to ride, meaning you’ll have to wait in line to board, especially at CBR.
At RIV you’ll catch the CBR-Epcot line to CBR, and you do have to transfer at CBR.