Which one is correct (no comma here) in class?
1. "I (no apostrophe here) am doing the roll [STRIKE]clall[/STRIKE] call." [STRIKE]or[/STRIKE]
2. "I am doing the register."
Note my changes to your layout above. When you give us options, please set them out as a numbered list. It makes it much easier for us to refer to them in our responses.
When I was at school, the teacher would have said "I'm taking the register". However, in order to use the present continuous, she would have had to interrupt actually taking the register in order to say the sentence! She would have been more likely to say, before starting, "Is everybody ready? I'm going to take the register now." Once she had finished, she could have said "I've taken the register".