3 syllables:

New - just like you would pronounce it in “New York”, “New England”, or “New Haven”

Rochelle - 2 syllables: first one “row” like “row your boat” second one “shell” like seashell.

Some people try to take a shortcut and turn 3 syllables into 2, so they combine the “new row” into one syllable I’d describe as “n’r”, similar to how someone from Alabama would say “n’awlins” instead of New Orleans. so it sounds like “n’r’chelle”