Los isn't conjugated — it's enclitic. That's the term for when a pronoun is attached to the verb.
Nothing changes for pronunciation. For the vast majority of speakers, that will be /o/. The letter o in Standard Spanish always has the same pronunciation regardless of stress or position in a word. Every o in los olorosos sounds the same.
Now...the handful of exceptions that as a non-native speaker you should avoid unless trying to specifically mimic an accent from a particular region.
For a few speakers in certain South American regions, via influence from other languages with a three-vowel system, that vowel will be /u/ (although those speakers generally pronounce all their /o/ as /u/).
Others as may adjust word or phrase final -o vowels to be a bit closer to /u/ (or even a swcha-like vowel), and in that case, because the los is enclitic, may be affected when its proclitic (unattached) form would stay a pure /o/.