The latter role he held for 16 years and gained a reputation for expert legal opinion, detailed and lengthy judgements and an adherence to precedent.
[2] In 1619 he was appointed nuncio extraordinary to Vienna and soon after was responsible for the arrest of Cardinal Melchior Klesl who had refused to act against Protestants after the Bohemian Revolt.
He was again named nuncio extraordinary to Vienna in 1622 to act as a witness to the marriage of Emperor Ferdinand II and Princess Eleonora Gonzaga.
The family later entrusted Verospi to negotiate the October 1627 marriage of Carlo's son Taddeo Barberini to Anna Colonna which he concluded to the satisfaction of all involved.
[2] In the midst of productive marriage negotiations, Verospi was elevated to cardinal on 30 August 1627 and was appointed cardinal-priest of San Lorenzo in Panisperna.