Grace, Mercy
This is one problem with Sola Scriptora and Sola Fides, if you notice the context of this verse:
Rom 5:10 For if, when we were enemies, we were reconciled to God by the death of his Son: much more, being reconciled, shall we be saved by his life. (Douay-Rheims Bible)
we were enemies, enemies of who? the next words answer this, enemies of God. How can we be saved by faith in God if we are his enemy? We cannot, but (at the risk of sounding like a Calvinist), we are saved by his grace, by the Son of God coming down from heaven and dying for our sins. There was no hope of salvation until the Cross.
God makes the first move in our salvation, the Father calls us to faith in Christ. This is an effacious (able to cause an effect, but not sufficient in and of itself) grace. Christ once and for all fulfilled the requirements that God set upon his people for the removeal of sin (see the rules for sacrifices in Leviticus). Christ is our Peace, Sin, and Guilt offering.
At least this is how I understand it (in a much abreviated form)