For a wall constructed with 2x4s, you would use aR-13 insulation because of the unusual heights of the walls there would be less waist to use rolls of R-13 that are 32' long covers 40 sq. ft.
To determine how much insulation needed you must calculate the total sq. ft. of all the wall space to be insulated. We need to know how long is the walls that is 10 ft tall. Is it 10' long or 16' long? That will determine the sq. ft. of that wall. Below are the possible calculations.
A wall that is 6' tall by 10' long is equals 60 sq. ft.
A wall that is 6' tall and 16' long is equals 96 sq. ft.
A a wall that is 10' tall and 10' long is 100 sq. ft.
A wall that is 10' tall and 16' long is equal to 160 sq. ft.
Now, total up the sq. ft. of your 4 walls and divide that by 40, then add an additional 4 rolls to compensate for cuts. If you have any extra full rolls you can return them.