In the Early Modern theatre scene, women were not seen on stage very often. Instead, boy actors would often portray female characters and the cast was generally all male. However, The Roaring Girl herself Mary Frith, was known to be a frequent face on the stage.specifically at the Fortune Playhouse. She often bantered with the audience on the stage, played the lute, and sang obscene songs (Royal Shakespeare Company).
And the play The Roaring Girl was no exception as it is thought that Mary Frith took part in one of the performances of the play, as is alluded to in the Epilogue of the play as found in the Folger edition of the play.
The Roaring Girl herself some few days hence
Shall on this Stage, give larger recompense.
Which Mirth that you may share in, herself does woo you And craves this sign, your hands to beckon her to you. (Epilogue, 3133-3136)
And while this was no irregular occurrence for Mary herself, when you look at the way theaters operated during the Early Modern period, it is a divergence from the norm fitting for the play.
Sources:
Middleton, Thomas and Thomas Dekker, The Roaring Girl. In A Digital Anthology of Early Modern English Drama, Folger Shakespeare Library. https://emed.folger.edu/roaring
Royal Shakespeare Company, THE ROARING GIRL,https://www.rsc.org.uk/the-roaring-girl