That's an important part of Dutch spelling. "Roze" is pronounced in a similar fashion to "rose-uh" but a word "rooz" (which does not exist) would be pronounced identically to "rose". It's a question of syllables.
In the word "boterham" we have bo-ter-ham, so we have a long o ("oo"), short e and short a. In the word "zeker" we have ze-ker, so we have a long e ("ee") followed by a short e. This is handily applied consistently throughout Dutch due to their many spelling reforms which have allowed for phonetic modern spelling.
I think you're mistaken WarmFoothills, the correct spelling of the colour is roze.
@niscate, rosé or roséwijn is the wine, the accent on the é is important, because it triggers a different pronunciation of the e. In spoken nobody would mix up roze and rosé, in writing this is possible, but it should be clear because there only is the colour roze and the wine rosé and rose without the accent doesn't exist. :)
Edit: BTW the flower called rose in English is roos in Dutch.