"Malus omnia in malum vertit, etiam quae cum specie optimi venerant"Seneca
God loves His sons and daughters. Because He is a loving father, He sometimes has to chasten His children so they keep going in a straight path. If He doesn't, then we are not His children but illegitimate, bastards (Hebrews 12:5-8). Worse, we are children of Satan (John 8:44) because we do not do the will of God, which is in our best benefit (Romans 12:2). As we fall short to His glory, and we don't repent, He gives us up to the Enemy, so we can experience the whole spectrum of consequences of our actions; that's what the parable of the Lost Son is about (Luke 15:11-32): He let us go to experience a self-conducted (as opposed to conducted by the will of God), godless life, but always waiting for our return so there can be celebration in Heavens. That explains why Paul in 1 Corinthians 5 and 1 Timothy 1 speaks about handing over people to Satan as a corrective experience: we are so stubborn in resisting the one and perfect will of God, that there is no other choice but to let us go for us to see the real dimension of what we wish to do. We want something so badly that we cannot longer hear the voice of God but the crave; we renounce His will so ours can take place, and we like it. And that is the essence of idolatry: to want, love something more than God Himself, to put Him aside so we do what we desire. He is so loving that He doesn't oblige us to do what He wants but let us go, it's our choice and He respects it. He is so loving He even waits there for our return to welcome us with arms wide open to His kingdom.
All that is what Romans 1 is about. People wanting something so blindly they forgot about God and engaged in what they wished to do. Knowledge, money, power, pleasure, anything... Those are not bad things. The Scriptures even encourage us to pursue those things (please, read the Song of Solomon before you misinterpret me holding some prude perspective). The bad thing is to want some of those more than God, because it'd break one of the two commandments we Christians have: love God above everything else. I think that would also explain why Paul says "for the pure, all things are pure" (Titus 1:15). People often take this passage as Paul talking about foods, but it says "all things", which I think includes circumcision and all other ceremonial laws. As Barnes noted: "The principle of the declaration is, that a pure mind - a truly pious mind - will not regard the distinctions of food and drink; of festivals, rites, ceremonies, and days, as necessary to be observed in order to promote its purity. The conscience is not to be burdened and enslaved by these things, but is to be controlled only by the moral laws which God has ordained. [...] But unto them that are defiled and unbelieving is nothing pure - Everything is made the means of increasing their depravity." As we do things that are sanctified, we can see the fruits of it, because sin always reveals its true nature (John 8:44).
So what the Christians in Rome did was apostasy. They liked what they did more than God, and it came with consequences. He didn't inflict a curse over them for their actions, He just gave them up to what was already there. We should avoid that: be so stubborn to God with something He doesn't have another choice but to leave us to experience the consequences.