I tried my B17 on my Roll and wasn't crazy about it. Went back to the stock seat which is OK.
That being said, I love Brooks saddles and would consider a B67 but don't want to put up the money if I end up not liking it on this type of bike. Do you think it is as comfortable and supportive as the stock saddle? You really do sit differently on this style of bike and need a different kind of backside support. I wish I had a B67 to try, but all I have are B17's.
I have a B17 on my road bike and have tried it on more upright bikes like the Roll. Definitely not the right combo for me at least. The B67 is made for more upright riding and its shape and width are similar to the "Cup" stock saddle. The Cup was comfy , but for me the B67 takes the comfort level of the Roll to a new level and it gives me good support. But that's my butt and you may not get the same results. Good news is that the B67 unlike the B17 requires little if any break-in period. Took me 6 months to break in my B17, but the B67 was comfortable out of the box and was broken in within a week or two.