Hello I just read your post and I know it is a few years old. I am guessing that you figured out how easy it is to sex a Rosy Boa by now. You do NOT need to have them probed. Rosy Boa Males have spurs and Females DO NOT. I know it is VERY tough to find the spurs on neonates, I have to use a large magnifying glass to make sure.
I hold the Rosy with the Vent side up, lightly bend/flatten out the tail section next to the Vent. Lightly take my fingernail and slide UP the scales right around the vent looking for a spur while looking through a good magnifying glass. Probing a Rosy does NOT need ot be done ever, and in my experience probing a Rosy is more of a chance of being wrong. I know other Boid species the male and female have spurs but this is not the case with Rosys. I decided to make these comments for any future Rosy Fanatics..
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