When I started I was told that EVERYONE eventually learns to roll, thought I'd be the exception. It took three months. I'd recommend you hold your sensei's advice and practice, practice, practice--VERY slowly, so you develop your form. Forty, fifty front, back, kneeling, standing. Good for the legs and you develop a keen awareness of where your furniture is.
BTW, a friend of mine started a few years after I did, I told him what I'd been told. It took him almost a year. He just successfully tested shodan at the age of 58 this spring.