You can chose Proofing paper for the roll selection paper and it uses gloss black - and then profile it - that is what is working for me using canon's new premium photo super-gloss 180gsm roll paper. I certainly did not want mat black, and this was the only choice for 17" rolls, as I recall, for gloss black and 17" roll. But it works fine for my eyes and images. In fact I don't even observe a difference printing with my profile or with the provided proofing paper profile and I expected that I would. At this point I do not know why, just that things are working.
The latest CS position about the media profiles seems to be that they are "descriptors" of paper types rather singular choices. I do know so far, taking that approach with them is allowing me to both work and get wonderful results...
And yes you are correct about borderless printing on 17" rolls for the described papers - just a note: all choices are for mat black.
My media guide shows broadly choices exist for rolls for borderless printing at the following roll widths: 10", 14", 16", 17" and A2.
There are actually 7 overspray areas. There is one at the far right just off the paper edge and from there they are spaced at 9.5", 12.5", 13.5" 15.5", 16.5" and 17.5".
I suspect that borderless is turned off on 17" rolls unless you have one of the Canon papers selected that support borderless printing on 17" rolls. According to the Media Guide, the 17" roll papers that support this are:
Premium Coated Paper
Premium Matte Paper
Fine Art Heavyweight Photo Paper
Fine Art Textured Paper
Fine Art Watercolor
Fine Art Block Print
There are other papers that are supported only at 16" rolls for borderless. It seems that Canon only allows you do do things based on the paper type selected and size selected.
I have run into a similiar problem trying to print on Moab Kokopelli 17" rolls using the Photo Paper Plus Semi-Gloss selection for the paper type. Unfortunately it won't let me select the roll feed with this combination. The media guide says that this paper is in sheets only.
At some point Canon is going to have to deal with the paper selection problem for those of us who print on other than Canon papers. I would be happy just to be able to modify an existing sheet type to allow it to print to rolls also.