So, if I understand correctly, you have dropped tiles on the grid to build some feature, say a room, and now you want to duplicate that whole feature in another place, also snapped to the grid. Your current process is to select that whole feature, copy it, then click the mouse approximately where you want the feature, and paste it. The problem is that all of the graphics that make up that feature are now misaligned to the grid and must individually be moved to match the grid again. Sound right? There's no solution for that problem built in to Roll20. There are ways to handle it with Mod (API) Scripts, but those require a game created by an active Pro Subscriber. I'm afraid building them and re-aligning them manually is the only option built into Roll20. You could use some external program (GIMP, Photoshop, Tiled, etc) to construct the features as a single graphic which could then be snapped to the grid.