Dutch as a language as a lot of vowels. Often the vowels are described in terms of short-long pairs, but technically, it is more correct to speak of lax-tense pairs. The tense vowels occasionally do have a slightly longer pronunciation it is hardly significant. The pairs are:
/ɑ/ - /a/
/ɛ/ - /e/ (/e/ in Hollandic Dutch generally diphtongized to [eɪ])
/ɪ/ - /i/
/ʏ/ - /y/ (although the lax consonant merges with /ə/ for a lot of speakers, including me)
/ɔ/ - /o/ (/o/ in Hollandic Dutch is generally diphtongized to [oʊ])
/u/ does not have a lax variant and /ə/ does not have a tense variant. If you really like to force the system, you could perhaps call these lax-tense pair, but there is no morphological alternation between the two, while with others, you sometimes find it.
But besides these lax-tense pairs, we have one actual long vowel, at least in the Standard Dutch pronunciation, which is only found in loanwords of French origin, for example zone'zone' is pronounced [zɔːnə].
Another worde that has this long lax vowel [ɔː] is the word roze [ʀɔːs/ʀɔːzə] 'pink'. But a fairly common pronunciation of this word is in fact [ʀɔːʀs] with a curious intrusive r phoneme.
How can we understand this development? It has to do with allophonic variants of the tense vowels in front of the consonant /r/ [ʀ]. In Dutch, whenever a tense vowel is placed in front of an ʀ in coda, the vowel becomes long, and in most cases changes the vowel quality changes slightly:
/a/
baat /bat/ [bat] 'benefit'
baar /bar/ [baːʀ] 'Give birth!'
/e/
beet /bet/ [beɪt] 'bite'
beer /ber/ [bɪːʀ] 'bear'
/i/
biet /bit/ [bit] 'beet'
bier /bir/ [biːʀ] 'beer'
/o/
boot /bot/ [bot] 'boat'
boor /bor/ [bɔːʀ] 'drill'
/y/
buut /byt/ [byt] 'the place you run to when playing hide-and-seek to touch be 'free' of being found, and to touch when you find someone when you are 'it''
buur /byr/ [byːʀ] 'neighbour'
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With this in mind, and specifically the allophone [ɔː] for /o/ in mind, we can understand the pronounciation [ʀɔːʀs] a lot better. The long lax vowel [ɔː] has simply not been integrated into the phoneme system of many Dutch speakers. As this sound was recognized as being audibly different to the speakers, they chose to form it with the allophone found in front of /r/. But as a result, the /r/ needed to be inserted to get the right allophone.And as a result, in many speakers' Dutch, we now find an intrusive /r/ in the word for Pink.