Is It Possible To Trade Before Rolling In Catan
No, you must roll before doing any trades or builds.
From the rules:

Turn Overview

On your turn, you can do the following in the order listed:


You must roll for resource production (the result applies to all players).
You may trade resource cards with other players and/or use maritime trade.
You may build roads, settlements or cities and/or buy development cards. You may also play one development card at any time during your turn.
After you’re done, pass the dice to the player to your left, who then continues the game with step 1.
Tip: For advanced players, we recommend combining the second and third steps. You can find more details in the Almanac under “Combined Trade/Build Phase.”