I am trying to understand IPA transcriptions in https://dictionary.cambridge.org/us/ when two words are involved. In particular, their rationale for changing some stresses, compared to the stresses in the independent transcriptions, when the words are put together.
For example, roller skate was transcribed as /ˈroʊ.lɚ skeɪt/. There is a space between "ˈroʊ.lɚ" and "skeɪt", and roller and skate were independently transcribed as /ˈroʊ.lɚ/ and /skeɪt/ respectively. This is intuitive to me: first word + space + second word.
Why the transcriptions are not always first word + space + second word, where first word and second word are the independent transcriptions, such as in the first example? Why the stresses changed in the transcriptions?