Login screens, roles, blogs and WPTouch

If the title sounds long and complicated, I agree but so is the mess I’ve got here. (WPTouch is the plugin to make screens work on mobile devices and disturbingly there appear to be whole forms missing when I use it with one, I’ll cover that in more detail if I have any wind left.) I’m kind of new to WP but certainly not to computing, I’m doing a site where I’m trying to do both a store and a blog. Now in my simple mind if I set “minimum role = Contributor” it seems to make sense that if you land on the blog page there SHOULD be some point where it asks you to log in, or asks you if you know that won’t work if you want to do a simple registration, because obviously if you’re going to be considered capable of writing I need to know who you are. Now I sort of think that’s likely provided automatically but maybe I have to stick it in myself, there is a “User Registration” plugin but distressingly when I put THAT in and activated it overrode my main site WP login screen and then I couldn’t get to admin, that’s NG! (And now I’m not seeing an internal WP user login screen AT ALL.) So understanding that whole concept and how I need to fix it is one issue, another is if I have all sample blogs thrown out if I click on “blog” from the homepage there’s link so I can start the first one, but if I do the same from a mobile device I get zero zip. Shouldn’t I see the same screen options on a mobile device that I do on my desktop, what is THAT is it deliberate or a bug? I know this is a lot but if someone can contribute even a PART of either of the answers it would be much appreciated.