This is the 8766th most frequent Polish word.
roszkowskim
"Roszkowskim" is the instrumental case of "Roszkowski," a Polish surname, meaning "with/by Roszkowski."
Here, 'Roszkowskim' is used in the instrumental case to denote communication or interaction with a person named Roszkowski.
Właśnie rozmawiałem z Roszkowskim na temat projektu.
I just spoke with Roszkowski about the project.
The word 'Roszkowskim' appears in the instrumental case to indicate association or company with the person named Roszkowski.
Spotkaliśmy się w parku z Roszkowskim i jego rodziną.
We met in the park with Roszkowski and his family.
In this sentence, 'Roszkowskim' is used in the instrumental case, contextualizing the act of accompanying or coming along with the person named Roszkowski.