During the years 1944 - 1946 he worked in the Obstetrics / Gynaecology clinic in Warsaw with Professor Adam Czyżewicz, after that, 1946 - 1951 he moved to Gdańsk as the professor’s assistant and then Assistant Professor at the Obstetrics / Gynaecology clinic of the Medical Academy with Professor Henry Gromadzki. His PhD thesis which he defended in 1946 (PAU 1945, No. 10,291) was entitled “The Blood Morphology in birth infections and its meaning in determining severity and prognosis”. His professorial thesis entitled “The thyroid and ovulation mechanism”, was presented and defended on July 8, 1947 before the Council of the Faculty of Medicine at the Medical Academy in Gdansk (“Polish Gynaecology magazine” 1948 No. 4). Associate Professor in 1953 and Professor in 1976. From 1951 - 1955, he was the Head of the Obstetrics and Gynaecology Clinic of the Medical Academy in Poznan on Polna Street. The Poznan Clinic was a large centre, but the organization of care for pregnant women was old fashioned. This involved a high mortality rate amongst mothers, fetuses and newborns. In a very short time Roszkowski introduced in Poznan and for the first time in Poland, "trauma meetings", discussing cases of complicated births. High prenatal mortality was due, amongst other reasons, to the fact that neither analysis of the reasons for death, nor autopsies of the fetuses and newborns were carried out. Roszkowski introduced changes in the care of pregnant and birthing women in his capacity as the national specialist on the National Council of the Polish Society of Gynecologists. In 1953 he delivered his paper “Methods used in the fight to reduce perinatal mortality” to the Council. Since then, analysis of the causes of death of fetuses and newborns is carried out by a team including obstetricians, neonatologists, pathologists, bacteriologists, immunologists, neurologists, biochemists and other disciplines, depending on the specific clinical situation. Perinatal mortality has been reduced sevenfold. Roszkowski organized the first Polish pathology of pregnancy wards, first in Gdansk, then in Poznan and finally the biggest ward in Warsaw on Karowa Street. In 1962 at the Conference of Polish Gynecologists in Gdansk he presented a paper on the programme entitled “Pathophysiology of fetal hypoxia”.