Assuming your question correctly I'll answer as follows:
Anything that can be dried to a bone or powder dry state can be milled into a 'flour' or just milled into whatever granular consistency you desire. So yes a tomato could be turned into flour. If you insist on using rejected tomatoes make sure to remove any bad spots before drying. Just remember that flour is a generic term in this case and is not like wheat flour or other milled grains. But could be added to a flour mix such as pasta or just as an additive for a sauce or soup for example.
So, Fully dehydrate the tomatoes, then figure the best milling method. I would use a coffee grinder to mill small amounts. It's not too consistent so anything substantial such as a pound or more might need something more towards the professional side and very expensive otherwise.