This has happened so many times when my coworkers are editing an unapproved or new email, instead of editing the email, they accidentally click on the link for the template of the email. I do not know why, but it does say template, but they still click on it assuming that that's what they need to edit. It would be nice if only marketo admins can click on the link, or move it at the bottom of the page or don't make it an active link.
That depends on how you want to manage your team's roles. You're an admin. You can setup new roles beyond the seeded ones that Marketo provides (the ones you listed above). Or you can edit the standard set to modify those roles.
If your non-admin users are all setup with the role standard user or marketing user, you can update those roles to disclude the ability to modify a template. Perhaps only a user with the role Web Designer (and admin) could edit templates. That's fine. It's all about what you want to do. I had more descriptive roles at my last company. Product Marketing had reporting rights, but not editing rights. etc..
I was able to edit the Marketing role, but not the standard. So I just changed the roles of all of the users who don't work with templates, not to have access to them. It's kind of strange when I tried to edit the standard user, it gave me a message that says standard user is a system role and cannot be changed. But the access appears to be the same as Marketing.