"Is God unjust who inflicts wrath? "

What do you think? 

Romans 3:5-6(NKJV)

But if our unrighteousness demonstrates the righteousness of God, what shall we say? Is God unjust who inflicts wrath? (I speak as a man.) 

Certainly not! For then how will God judge the world?

To answer this question many people will focus on whether a loving God can inflict His wrath and still be just.  I think that is a backwards way to approach the question. 

I think the proper question is "is God a just God"?  To answer that question we need to look at the definition of just.

just1

1. guided by truth, reason, justice, and fairness:

We hope to be just in our understanding of such difficult situations.

2. done or made according to principle; equitable; proper:

a just reply.

3. based on right; rightful; lawful:

a just claim.

4. in keeping with truth or fact; true; correct:

a just analysis.

5. given or awarded rightly; deserved, as a sentence, punishment, or reward:

a just penalty.

6. in accordance with standards or requirements; proper or right:

just proportions.

7. (especially in Biblical use) righteous.

From <http://www.dictionary.com/browse/just>

In looking at the definition I'd answer that yes God is a just God.  It is part of His character.  I'd say Scripture shows that He is guided by truth, reason, justice, and fairness. 

So the way I see it, since we have established that God is indeed just then we have to concluded that the actions He takes are indeed just.  Therefore it is just for Him to "inflict wrath".  Make sense?