Thoracic rotoscoliosis means that there is a curve in the thoracic region (chest) that has a component of rotation in it.
Usually, all scoliosis (curvature of the spine) has a little rotation in it, so in many cases, it is just shortened to scoliosis.
As to the significance of this findings, you need to speak with your physician.
But, usually, curves are not considered "scoliosis" until they are at least 10 degrees. In some institutions, they do not call a curve scoliosis until it reaches 20 degrees, because they do not want to label a patient, who may then have trouble getting insurance later on, or an adolescent who may want to enter the military in the future. They call the curves from 10-19 degrees spinal asymmetry.
Treatment of a curve depends upon its size, location, and skeletal age of the patient.
So, again, you need to speak with your surgeon/physician to see if this curve is significant.