Van Roomen was born in Leuven, the son of Adriaan Van Roomen and Maria Van Den Daele. He became a professor, and then travelled extensively in Europe.
After studying at the Jesuit College in Cologne, Roomen studied medicine at Leuven. Roomen was professor of mathematics and medicine at Louvain from 1586 to 1592, he then went to Würzburg where again he was professor of medicine and became "Mathematician to the Chapter". He met Kepler, and discussed with François Viète two questions about equations and tangencies. He then spent some time in Italy, particularly with Clavius in Rome in 1585.
He was ordained a priest in 1604. After 1610 he tutored mathematics in Poland.