I have great luck spraying large prints outside provided they are in the vertical position. For some reason, I almost never have problems with crud. Although for about a week in the Spring little tiny saturated-color-loving flies can drive me nuts.
Yes, that roller holds a lot of paint. For periods of 2 or 3 days you can put the entire roller + handle in a 1 or 2 gallon freezer bag, get out the most air you can before sealing. A 2.5 gallon bag holds an entire 9" roller + handle. Maybe add a couple drops of water. For long periods you can wrap up the wet roller tightly in some clinging food-wrapping tissue.
FWIW I find I can get very nice spray coated prints using about 1/2 the paint I need for rolling, even when I preserve the wet roller between sessions. Takes about 7 ml of Glamour II concentrate (which is 10ml of diluted solution) to richly coat a square foot of print.
Also, spray cans of Clearjet FA2000 and AFA2000 can coat a canvas outdoors that can be taken back inside after just a couple minutes. However, be sure you keep those recently coated prints in a room with an open window and a door that can be closed to the rest of the house, takes a few days to lose the stink.
