What you need to do here is cast the “OtherActor” to something in order to differentiate it from pickups. Preferably your obstacles are instances (or childs) of a shared class “BP_Obstacle” for example.
Then draw a cast to BP_Obstacle from the “OtherActor” pin and only if the cast succeeds, you explode the rocket.
(Or you do this in the BP_Obstacle Overlap event like KalemRose suggested)
If they don’t share a class you could try turning this around, for example if you overlap things that are not pickups (eg. cast to pickup fails) you consider them an obstacle.
Lastly you could also use custom collision channels.
Hope I could help you with this!
Cheers 