Stock tires on a 2007 Roadking were MT90B16 72H front and MU85B16 77H rear. The rear tire dimensions were 25.71" outside diameter, 5.51" overall width.
The MU rear tire is roughly equivalent to a 140 metric size designation. Others have indicated that they had installed a 150 on their '04-'08 Touring models without issues, but you will want to do some measurements on your particular bike to make sure you have enough clearance. The Commander II 150/80B16 77H measures 6.5" wide at the widest point, versus the stock tire at 5.5" wide. So you will need to measure clearance on each side to parts like the swingarm, rear belt, belt guard, fender, etc. Measure the clearances with the stock tire, then determine if you have enough clearance to allow for the wider tire. There is also a difference in outer diameter, with the Commander II coming in at 26.06" OD and the stock tire at 25.71" OD. One other factor is the rim width. Stock rims are 3.0 inches wide. I couldn't find a spec from Michelin for the recommended rim width for that 150/80 B16, but it is likely it really calls for something 3.50" or wider.
Jerry