To jump into Romans 6, and the question asked in verse 1, without first knowing the theology that Paul outlined in chapter 5 could, potentially, lead to missing a major point of God's Word.

In chapter 5 Paul makes clear that only Jesus Christ can save the ungodly from the Wrath of God - Christ died for the unrighteous and by His Blood many were made righteous and given the free gift of eternal life by God's Grace. Where sin abounds, Grace abounds MUCH MORE! Those IN CHRIST are no longer under Law, but are now under GRACE!

The rhetorical question posed by Paul in Romans 6:1 in paraphrase is, "if I'm under Grace, not Law, it's no big deal if I sin, right?"

If a person is asking this question from the vantage point of wanting license to sin it shows their enslavement; after all, we are all slaves, the question is, what are we enslaved to?