An apparatus for carrying out a block-change in a ring spinning machine, in which a block of roving bobbins which each supply an associated spinning station are changed together when the rovings wound on the bobbins run out. Preferably, more than one block of roving bobbins is provided. The roving bobbins used to form a block are combined in such a manner that all of them have at least substantially the same length of roving wound on them. The end of the roving on at least one of the bobbins of the block is detected before that end passes through the associated drafting unit, and the block-change is triggered at an instant of time when the roving end has not yet passed through the drafting unit.