3 Nephi 9:15 -
Behold, I am Jesus Christ the Son of God. I created the heavens and the earth, and all things that in them are. I was with the Father from the beginning. I am in the Father, and the Father in me; and in me hath the Father glorified his name.
All things. It astounds the mind to think of all the things there could possibly be that were created. Our Lord is most capable, but I don't think He did it alone. Not that He couldn't. But I think He wanted all of us to be a part of creating the world we would live on, and be tested on. I think (and this is not doctrine) that He wanted us to feel a stronger connection to the world. To have deeper meanings and joys with certain creations--able to find the beauty in them more easily than we do in other things. My friend had a teacher who once suggested they had a part in a creation, and she is sure she helped to create dolphins because she loves them so much. I've often wondered what I helped with, which things I love so much here. Seahorses? Turtles? Roses? I'll never know in this life, but it doesn't fully matter to me--as I find the greatest joy and fulfillment in the beauty of landscapes, clouds, rainbows, various weather, and more.
While I may speculate on our role in the creation, I do not speculate in the fact that we had one. For it is backed up by the scripture in the Pearl of Great Price, Abraham 3:24 -
And there stood one among them that was like unto God, and he said unto those who were with him: We will go down, for there is space there, and we will take of these materials, and we will make an earth whereon these may dwell;