He spans both eras.
A classical music composer (in the romantic style).
classical and romantic
Rossini lived during the Romantic Era, although his music is said to have a link between the romantic and classical periods.
I believe you mean the William Tell Overture by Rossini.
If you are referring to Gioachino Rossini, he was a Romantic composer, not a painter. He composed over 39 operas, including William Tell and The Barber of Seville.
After 10 seconds of google-ing I found your answer... ... yes, Rossini was an Italian composer.
Cioachino Rossini was an Italian composer.
Gioachino Rossini
Gioachino Rossini belonged to the early 19th century, primarily during the Romantic era of classical music. His most active years spanned from the late 1810s to the 1830s, during which he composed many famous operas that influenced the development of the genre. Rossini's works, characterized by their melodic richness and innovative orchestration, laid the groundwork for future composers in the Romantic period.
Opera music composer
The opera 'William Tell' was composed by Rossini. That included the overture, of course.
If this is about the composer, its Gioachino Rossini.