Yes, this can hold a Mega Roll.
Hello Nan and thank you for your interest in Moen products. The model number for the Moen Kingsley Pivoting Double Post Toilet Paper Holder in Wrought Iron is YB5408WR. If you have additional questions, please feel free to call us at 800-289-6636. Our business hours are 8:00 am – 7:00 pm Monday through Friday (EST).
This is a pivot bar, so there is no roller portion. The middle section lifts up to change the toilet paper roll.
I would not recommend mounting this holder vertically. I think it will swing open.
Never had any problems with large rolls of toilet paper.