Can't use netting to keep out insects, insects are required for many vegetables to produce. There are other ways to control insects. Start up for a decent garden can be expensive, to create the right enviroment and such, they take a lot of work and time to maintain and produce but they are well worth it if one knows what they are doing. Stop watering your grass, there is no need to waste water on them unless required in some manner. Never heard that about shingled roof systems, you should research it as opposed to going by what you heard. Gardens are a labor of love, if you don't enjoy them, you wont put the time in, you won't get the rewards.