Course-level roles are roles with permissions set at the course level. Usually these roles cannot see more than what is in the course.
Students [Default] have the ability to submit assignments and that should never be taken away from them. Students have some restricted permissions, but they have enough permissions to use Canvas. Sometimes students may have other permissions bestowed upon them, if the an admin gives them more permissions.
TAs [Default] are very similar to teachers in the sense of permissions, except TAs should not have access to SIS data. TAs are meant to help the teacher and provide support. Admins can grant certain permissions to TAs, like grading, or not allow the TA to grade. It depends on the institution and what the needs are.
Teachers [Default] can have almost account-level permissions. Teachers are basically course admins and have control over the course. However, like all the roles, they can be used as a different type of user, if needs be.
Designers [Default] should have access to at least using the course content, creating discussions, announcements, assignments, quizzes, and other content filled features. Designers cannot access grades. However, if your institution does not use Course Designers, you could use this user role as another TA user role that has more permissions than the regular TA.
Observers [Default] can be linked to a student enrolled in a course. For example, parents, guardians, and/or mentors may wish to be linked to a student to view the student’s progress in the course. Usually observers have the least amount of permissions.
Course Copy [EOU] can perform course copies which allows them to see assignments, discussions and quizzes. However, they cannot see grades, submissions and people. This role is to help facilitate course copy needs without allowing the person to see vital information.
Discussion Only [EOU] is a special role designed to allow students from one course to participate in a discussion from another course. A person with this role will not be able to see or submit anther type of assignment. Only discussions.
Visitor [EOU] have limited visibility within your course. They only have view capabilities within the course. Visitors cannot see grades.
A screenshot of the permissions can be found here.
Please see the Canvas Guides for more information about Roles.
* [Default] designation identifies a role created by Canvas.
* [EOU] designation identifies a role created EOU.