"What, then, shall we say in response to these things? If God is for us, who can be against us?"
What is God saying?
When trying to figure out the complicated things happening around us, we can have the assurance that when we are on God's side, there is nobody that can defeat us.
What is God saying to us today?
We often can get the point of this verse inverted. We think that if we can get God on our side, then we will be invincible. But, it's not a matter of getting God on our side, it's about us getting on His side. And, even when we are on His side, that doesn't mean that our life is going to be perfect. The Bible is filled with examples of people who were on God's side, yet experienced horrific things. So what is God promising in this verse? It's not the guarantee of indestructibility that the prosperity "gospel" teaches, rather God is saying that His side is going to have the ultimate, eternal victory. Since God's cause is going to triumph over the darkness of sin, if we join Him we know that we will be victorious as well, since our cause will match His. And we can take comfort in that, while we might be defeated in this life, in the end we will win!
What is God inviting us to do?
He is telling us who will be the winners at the end of the story, so it's up to chose what side we want to be on. Will we choose to be on God's side and have the assurance that we will be victorious in the long run? Or, we will we choose to be on the side that ultimately loses? God invites us to enjoy the guarantee of victory by uniting with Him today.