Van Roey participated in the Conversations of Mechelen, a series of ecumenical dialogues between clergymen from the Roman Catholic and Anglican Churches hosted by Cardinal Désiré-Joseph Mercier, from 1921 to 1926, but for which he was less supportive.

[2][3] He received his episcopal consecration on the following 25 April from Archbishop Clemente Micara, with Bishops Gustave-Joseph Waffelaert and Gaston-Antoine Rasneur serving as co-consecrators, in the Cathedral of Mechelen.

Cardinal van Roey intervened with the authorities to rescue Jews from the Nazis, and encouraged various institutions to aid Jewish children.

One of his acts of rescue was to open a geriatric centre in which Jews were housed, at which kosher Jewish cooks would be required who could therefore be given special passes protecting them from deportation.

[8] On 24 September 1942, van Roey and Queen Elizabeth of Belgium both intervened with the German authorities in Brussels after the arrest of six leading members of the Jewish community.

Van Roey presided over the marriage of Prince Albert and Princess Paola Margherita Consiglia Ruffo di Calabria on 2 July 1959, and of King Baudouin I and Doña Fabiola de Mora y Aragón on 15 December 1960.

[11] Van Roey, who had long suffered from a circulatory illness,[11] was administered the last rites and Communion by Bishop Leo Suenens on 5 August 1961.