The growth of the power of the Rosentals at the end of the 15th century was also beneficial to the townlet of Blatná. In 1489, right after Zdeněk Lev of Rosental, the most powerful member of the dynasty, took over, the townlet reconfirmed its older privileges with the addition of the right of escheat for burghers. This was followed by other privileges. In 1502, the townlet gained the right to hold two annual markets, in 1513, it received a brewery and a church with a rectory for its own use, in 1514, it was granted the right to seal with red wax and to build a fence around the townlet, which, however, would never occur. The last document, dating back to 1529, was issued to move the date of one of the fairs.
The aim of Zdeněk Lev was certainly to support his townlet, which was not only his property, but also his residence. This was also indicated by the construction of a Gothic church with a cellar vault in 1515 or by the invitation of the builder Benedikt Rejt, who would rebuild the southern wing of the Blatná castle between 1523 and 1530. The large amount of the rights granted can also be explained by the financial needs of Zdeněk Lev, who would certainly not give these rights out of mercy and friendship with the townspeople, but in return for compensation in the form of a financial injection. His position as the second-hand man of the king, i.e., the burgrave of the Kingdom of Bohemia, was very costly and, after his death in 1535, his son Adam Lev of Rosental suffered the consequences.
He took over the indebted estate, whose wealth was based on its status and debtors, but not on cash to cover its own debts. In 1539, he managed to commission the casting of the largest bell called ‘Mother of God’ (Czech: Matka Boží), but two years later the townlet received the last privilege to establish a town hall and to impose taxes on fairs, for which they had the right to have armed men of their own. This was probably the last attempt to raise some cash for debts in exchange for the sole benefit that a nobleman can offer: a privilege. In 1541, Adam Lev was forced to surrender Blatná to the largest creditor Adam of Sternberg. Adam Lev and his whole family moved to Moravia and the Rosental dynasty would never return to Blatná, which was now endowed with privileges and assets enabling its further growth.