For when you were slaves of sin, you were free in regard to righteousness.  But what fruit were you getting at that time from the things of which you are now ashamed? For the end of those things is death. (ESV)
Paul is being a bit facetious here. When you were slaves of sin you were free? Free in regard to righteousness. In other words, there was no righteous standard that you held yourself to. You followed your master, the Devil. You were free to plunge yourself deeper and deeper in sin while rebelling against God's holy standard.
I can hear Paul saying, "How was that working out for you?" It is amazing how many people cling to their life of wickedness thinking that they are truly free when the opposite is true. Paul raises the question concerning what fruit came from that life of shameful behavior. It might be helpful to take a quick look at the fruit of sin.
Imagine that young man who makes a priority of being with as many women as he can. He does not love any of them. He uses them. They are objects to him. Notches on his belt. He is "free" to satisfy his lustful desires. What is the fruit of that lifestyle? No lasting relationship. If he has children he has shown them they are not valuable, just the offspring of lust. Ultimately, his sin brings no satisfaction.
You can supply any example you like. We can look at rock stars and movie actors who fill their lives with the pursuit of pleasures. They have everything that money can buy. Do they have deep lasting joy in their lives? No. In fact, it is not surprising to hear of a person who has gained all of the world's pleasures committing suicide. The end of the pursuit of freedom outside of Christ is death. Eternal death.
Christian friend, do not idolize the things of the world. The pursuit of them leads to death. The fruit of a sinful life is shameful and unsatisfying. Pursue Christ with all that you have.