Hi there Phazel.
to my understanding the creation mentioned in Roman's 1:20 has got nothing to do with rocks or trees, although I'm sure there are lessons to be learned from those as well.
I believe that in this verse the creation mentioned here is us.
Rom 1:20 For the unseen things of Him from the creation of the world are clearly seen, being understood by the things made, both His eternal power and Godhead, for them to be without excuse.
I have a two and a half year old son who has been and incredible blessing to me and has opened me up to a lot of new understanding as well, especially of this verse.
There is another verse that I think can help us to understand Roman's 1:20
Mat 7:8 For everyone who asks receives, and the one who seeks finds, and to the one who knocks it will be opened.
Mat 7:9 Or which one of you, if his son asks him for bread, will give him a stone?
Mat 7:10 Or if he asks for a fish, will give him a serpent?
Mat 7:11 If you then, who are evil, know how to give good gifts to your children, how much more will your Father who is in heaven give good things to those who ask him!
In other words God is the perfect Father, so if you love your children and your evil, selfish, fleshy men, how much more loving is God than earthly parents!
What's this got to do with the above verse?
I believe what Roman's 1:20 is saying is that God has created us in such a way that whilst we a not a finished work yet, we still bear some of His characteristics for example most people if they saw their child about to be run over by a car, they would not hesitate to dive in front of that car to save them, even if it meant certain death.
God's love for His children is not different from ours, it's just better, stronger, more pure and far superior in every way!
In other words, God's love for His children can be clearly seen in an earthly father and son relationship, same goes for all other relationships as well.
So if you wouldn't consider for a half a Milli second roasting you son of daughter alive for all eternity or even 1 second then where would you get the idea that God would do that to His beloved children?
Can you see now why I linked these to verses?
When God creates its just like any other artist (with integrity intact) He creates from himself, from what's inside.
Jam 3:11 doth the fountain out of the same opening pour forth the sweet and the bitter?
Mat 12:35 The good man out of the good treasure of the heart doth put forth the good things, and the evil man out of the evil treasure doth put forth evil things.
Nice to meet you phazel and I that helps and doesn't confuse you more!