The first passage traces the consequences of suppressing the truth about God and swapping him out of your God slot and swapping in some dodgy replacement component instead (aka, idolatry). The consequences of sin get worse as the argument progresses. The last bit of the process finishes with God giving people over to a messed up mind. At this stage a person is not only sinning, but doesn't even recognise it as sin any more.
In contrast, Romans 12:1-2 talks about the renewing of minds. It's something that comes along with God's mercy. It seems God not only forgives sin but also undoes some of the damage it's done to us.
An point for discussion though: How can Paul command you to have something done to you? He commands you to 'be transformed'. It's in the passive, so what's Paul getting at?
Thoughts?