I think if you set up rocketbook to just output the image the @kellerjustin s app will take care of the OCR and upload it into Joplin. Although I can imagine that rocketbook might have a better OCR engine, so having the importer grab a pdf or something is probably better.
His app is on github so you could probably update it to handle the pdf/text pair. Should be fairly simple to get exactly what you want.