tami7326 I tried to reproduce your issue in my testing user folder where I have never had any mods or CC. I had no problem with locking up or saving nor any problem with placing, adjusting or moving the round roof on the round structure I built to test the roof. So, my suspicion is that your mods or CC may still the be the cause of what you had happen if you were building in a save where you had played or built in before removing the mods and CC. Some mods and CC can still affect a save it was in even after if you remove the them as they may have left something behind in the save. Those type of things can linger long after the mod or CC item that leaves them has been removed. You won't be able to get rid of them except by starting a new save.
So, my suggestion for you is do what I do. I created a separate user folder that I only use for building only. I don't have any mods or CC in that folder. I have only one sim in the save so I can test the build after it's done so I can make sure I don't have any route blocks, etc. that might show up in live mode later. Then I save the build to my Library. Then I transfer the files in the Tray folder in my build user folder to the Tray folder in my main user folder where I play so I can install the build into my main save. After transferring the files, I make sure I leave the Tray folder in the build user folder empty. If I want to place any CC in the build, I place it after I get the new build in my play save. I find that doing it that way works much better as I have fewer issues like you and others run into when building in the same save that they play in. There is one big advantage to doing that too if you don't delete all the sims as I have. Since all your builds will still be in the same save, if you have a major issue in your play save or get a bug that corrupts your play save, you can copy your build save to use as a starting point for a new save, so you don't have to install all those lots. I can't do that since I deleted all the premade sims and NPCs in mine. But if you don't delete any of the sims and turn aging and Neighborhood Stories off when you start the save, you can.
Hope this helps.