You asked

what did 'thrones, dominions, principalities, powers' mean in roman era cosmology or philosophy?

The passage, plainly, with room to sit with it.

Colossians 1:16

“For by him were all things created, in the heavens and on the earth, visible and invisible, whether thrones or dominions or principalities or powers: all things have been created through him, and for him.”

The Apostle Paul is writing to a community of Jesus-followers in Colossae, a city in Asia Minor (modern Turkey). He's emphasizing the supreme role of Jesus Christ in all creation and in salvation, perhaps in response to beliefs that were diminishing Jesus' unique authority.

What does it mean for you that everything, visible and invisible, is said to be created through and for Jesus?

Keep thinking

Read alongside it

Ephesians 6:12
This passage also speaks of spiritual forces and authorities, framing them as a challenge believers face.
Romans 8:38-39
Paul lists various powers that cannot separate believers from God's love, including 'principalities' and 'powers'.
John 1:3
This verse from John's Gospel similarly states that 'all things were made through him' (referring to the Word, Jesus).

Ask your own follow-up