The LEDs will run on anything from 5 V to 6 V with no problems. The problem is the batteries. If there is no AC power available and you don't want to go with a solar panel battery charging system, then you're gonna pay a lot for batteries.
Another approach is to go with a 12 V battery and a high-efficiency buck regulator. Even with the power loss in the regulator, this will let you get a lot more of the energy in the battery out in a useful manner (no brightness fall-off). 2 rolls = 5 W, times 3 hrs / day = 15 Wh per day. With a nominal 12 V battery, you need 1.25 AH (amp-hour) battery capacity per day between charges. If you have two batteries and rotate them once per week, you need a 12 V, 9 Ah batteries. Stop in to Batteries+ to get a feel for the size and weight of these things.
Questions:
Rechargeable or not?
How many days on one set of batteries?
Anything else we should know?
ak