This case has been shelved by our engineering team. Should it be reopened, this issue will be updated.
Roll call can fail to load with a 504 Gateway Time-out in courses if it takes too long to load the data.
Roll call should load successfully in courses.
Prerequisite: Have a course with a decent amount of enrollments, about 500, with each enrollment in multiple sections. In my example it is 559 students in each of the 5 sections.
Attempt to load the roll call tool. If it loads successfully, you may need to throttle your network.