Sometimes older rosys get those fatty deposits. It not a health problem but he/she does look skinny. Maybe feed it a bit more..

Fatty deposits can be developed from the snake not being put on a regular feeding schedule. Then what happens the animal tends to store fat for those long fasting periods. Give it a healthy size mouse as often as possible. Also keep the water dish out of the encloser right before and then several days after a meal. Rosys that drink right before or after a meal can regurge.