This is the 846th most frequent Dutch word.
mooiste
"Most beautiful"
'mooiste' functions as a superlative adjective modifying 'huis' to indicate it is the 'most beautiful.'
Dit is het mooiste huis dat ik ooit heb gezien.
This is the most beautiful house I have ever seen.
'mooiste' refers to 'moments' as being the pinnacle scenario, showing an absolute and qualitative state.
De mooiste momenten zijn vaak onverwacht.
The most beautiful moments are often unexpected.
'mooiste' is part of a comparative clause describing 'roos' as the superlative member in comparison to other flowers.