It looks like there is no validation happening when you upload course via csv and specify enrolment method (currently supported are manual and self). So if you upload smth with valid role like

shortname,fullname,category,enrolment_1,enrolment_1_role

c1,course1,1,manual,teacher

you will have enrolment instance with teacher role. But if you try smth with invalid role like

shortname,fullname,category,enrolment_1,enrolment_1_role

c2,course2,1,manual,teacherfdshfkj

A course still will be created, no error/warning will be shown and you will have enrolment instance with student role.

I think we should at least notify user that there is some bad data in csv. And may be its better to not allow the creation to happen at all.