Did I miss something? I've never seen a "backpack" 1 gallon B+G pesticide sprayer. Anyway, my question is how serious are you, when you say: "seeing a few roaches . . . every so often inside"? Roaches aren't solitary insects. And broadcast treatment isn't the way to deal with them (neither is spraying lots outside, if they're living inside). Does your pest control company use baits and gels? Spiders are a completely different story. You need to caulk where they're getting in, and just vacuum them up when you find them inside. You won't get a colony of spiders taking over your house (unless it's already filled with other insects), and no amount of chemicals (that don't kill the human occupants too) will prevent a single insect from walking in and making itself feel at home.