For portraiture most people want a normal lens and a short telephoto. I used a 110mm and a 180mm on my RZ67. To compare to 35mm or full frame digital you divide by 2 to give you the focal lengths of 55mm and 90mm. The 110mm is not available for the RB but there is something close to the same focal length available.
Most landscape photographers like wide angles. The 50mm or 65mm are both nice. It just depends on which focal length you prefer.