1. find out After which sound you always end with rolling R. 2. practice, and force your tongue to be straight, not curve up .
for Famous, I guess you pronunce as Famour.., so push your toungue to touch the bottom teeth. so it won't curve up.
For Fall, you can pull your tongue out of mouth for the "L" sound. because it is acceptable to prounce it in two way, pulling it out or touch the upper teeth. This way, it will force you tongue to be straight. After a while, then you can switch back to the normal/canadian way :)
for Famous, I guess you pronunce as Famour.., so push your toungue to touch the bottom teeth. so it won't curve up.
For Fall, you can pull your tongue out of mouth for the "L" sound. because it is acceptable to prounce it in two way, pulling it out or touch the upper teeth. This way, it will force you tongue to be straight. After a while, then you can switch back to the normal/canadian way :)