Markets have lauded Rostowski, born in Britain to Polish exile parents, for the fiscal discipline he has enforced, but his ministry is struggling to deal with an economy slowing much faster than expected and budget revenues which, for the year to date, are far below forecasts.
Tusk also said that Foreign Minister Radosław Sikorski would be a good fit for a big international job.
In an interview on Polish television station TVN24, Tusk spoke about jobs falling vacant between now and spring 2014, which he said included the role of NATO secretary general, United Nations secretary-general, president of the European Commission, head of the European Council, and EU high representative for foreign affairs.
"We do not lack good names. I think that both the NATO secretary general and the high representative, meaning the foreign minister, are very interesting spots," Tusk said.
"Minister Radek (Radosław) Sikorski comes as an obvious candidate, but also Jan (Jacek) Rostowski, Jan Krzysztof Bielecki, I could list many Poles who have full qualifications to take the highest positions, Jerzy Buzek."
Bielecki is a former prime minister who is now a senior economic adviser to Tusk, while Buzek, another former prime minister, has served as president of the European Parliament.
On Monday Tusk squashed speculation that he would launch a bid to succeed José Manuel Barroso as European Commission president, saying instead he would lead his party into the next election in 2015.