Rosol was made to work hard for his second career singles title, as Janowicz pushed him all the way in a 3-6 7-6 (7-3) 7-5 victory in North Carolina.
It denied Janowicz his maiden title on the tour but moved him up the rankings regardless.
While world number 27 Rosol enjoyed a six-place boost, Janowicz rose nine spots to 43rd in the world.
Rosol was required to see off Lu Yen-hsun in the semi-finals and the 31-year-old from Chinese Taipei moved up to 34th as a result of his last-four appearance.
Petra Kvitova's second success at the Connecticut Open was not enough to move her any higher, as she remains fourth in the world ahead of the US Open this week.
Samantha Stosur was beaten by Kvitova in the semi-finals at Connecticut but climbed four spots to 21st in the world while Camila Giorgi jumped to 31st.
The Italian also reached the semi-finals in New Haven and moved up seven places as a result.