RNAlater is a non-lysing non-fixative reagent, and you may get some viable cells from the stored tissues after removing it by consecutive washes or blotting or dialysis. But RNA pool is going to be all messed up right after the removal, so you might need to culture the cells for a while to make sure that all post-storage effects are gone. However, if you are interested in RNA profiles as they were on the moment of tissue preservation, you cannot go through revitalization step. You have to isolate RNA while keeping cell metabolism shut down.

As per protocol for the latter case, you may take a look at the following paper: "Time-course RNAseq data of murine AB1 mesothelioma and Renca renal cancer following immune checkpoint therapy" (2024), doi: 10.1038/s41597-024-03294-0 . At some point, the authors evaluated the effect of RNAlater on scRNAseq output (see "Comparison of tumor dissociation protocols"). Since you already have your tissues in RNAlater, you may try to dissociate them using RNAlater as a dissociation medium, and then pellet the obtained single cells and wash them with cold PBS by re-pelleting. Alternatively, you may quickly rinse the tissues with cold PBS and then proceed as described in the above protocol (dissociation in PBS - single cells sedimentation - RNA isolation). Note that the authors observed an RNAlater-associated bias in RNAseq profiles, which is not particularly surprising. Depending on your goals, you may handle such a bias using proper controls.