For years, thousands of Roseville residents have spruced up their lawns with crabapples, persimmons and other free trees from their Urban Forestry Foundation. But merchants and their landlords haven’t been enthusiastic. They want to preserve their visibility, and fret about maintenance costs. Now the Foundation is appealing to them with shade trees, funded primarily by Roseville Electric, because trees reduce electricity consumption. They’re also armed with a university study showing that shoppers like tree canopies, and part with more money than at barren shopping areas.