This is the 1872nd most frequent Polish word.
mają
"Have" (third person plural form).
In this sentence, 'mają' is used as the third person plural form of the verb 'mieć', which means 'to have', indicating possession.
Oni mają psa.
They have a dog.
Here, 'mają' describes a characteristic or feature possessed by the roses, as part of the plural subject.
Róże w ogrodzie mają piękne kolory.
The roses in the garden have beautiful colors.
In this context, 'mają' conveys the state of having an arranged or planned event in the future.