Can a employer change your title and respon (demotion) and still require you do current respo w/o you agree?

This company fired a bunch of people then took other staff and demoted them to fired postions BUT required those employees to continue to do their current position in addition to the demoted position. No change is pay (grossly underpayment as is). These were hourly people - most are very upset and looking for other work but is what the co did legal - can yuo take someone who is say a bookkeeper and tell them your now the janitor but you need to do the bookkeeping too?