From Longman Dictionary of Contemporary Englishsomething is not a bed of rosessomething is not a bed of roses (also something is not all roses British English) informalPROBLEM if a job or situation is not a bed of roses, it is not always pleasant and there are difficult things to deal with It’s no bed of roses teaching in a secondary school. → rose
Examples from the Corpus
something is not a bed of roses• Our marriage hasn't been a bed of roses. 