If I have a Senior Freeze, will my taxes increase if a taxing district “rolls up” their millage?

Yes
If a taxing district “rolls back” their millage, you will see a decrease in taxes from that district.
If the taxing district “rolls up” their millage, you will NOT see a decrease in taxes from that district.
Although your tax bill may be the same as last year, you will not see the savings of tax dollars you would have enjoyed had the taxing district “rolled back”.