Don't block it. Do this in a blank plan and make a symbol of it instead of a block and save that to your library. Once doing this, it will work like you want. BTW, I would save that plan that you made it in so that you can come back at a later date to modify it if you want.
The only thing I can think of is to select a roof plan> transform/replicate it and move it so that you can see which baseline is moving. If it's one you want to delete, delete it, if not hit the undo and select the roof plane again and tab to get the next one. Kind of a process of elimination.
Here's another way. You can make any electrical item like a light, switch, outlet, etc. be placed on anything you want. Open Chief's library to the fixture you want. First copy that fixture to your user library. Don't place it in the plan first. It won't work. Now you can open the symbol (not open item) from the electrical item copied to your user library. You can not do this while it is in Chief's library. Once open, make it sit on the floor...not on the wall. Now you can place it in the plan and it will be free-standing and you can rotate it or whatever. In plan view, place the symbol so it looks correct in plan view and set the height. Now take an elevation. Select the item and "open symbol". Now set the origins so that it looks right in 3D. Done. I know it sounds like a lot but I did the one in my attachment in around 30 seconds. Once you understand and do it several times, it's real fast to do. I already have electrical items in my user library ready to go. My image has a light fixture on a slab column.