I want to suggest here that Romans 16:20 implies the imputation of the active obedience of Christ. I'll be assuming much of G.K. Beale's work on the Temple and his Biblical Theology here. Brandon Crowe's "The Last Adam" is helpful here, too. I'm also assuming an amillennial interpretation of some verses.
"And the God of peace will soon crush Satan under your feet".
That is a very short verse, but it is rich with biblical theology. Of course, the verse echoes Genesis 3:15 and the promise that the seed of the woman would crush the head of the serpent. Adam himself was established in Eden as a King-Priest who was to guard the sanctuary-temple of the garden of Eden. Anything unclean that entered was to be judged by Adam in covenantal obedience to Yahweh. Adam failed in his task, allowing Satan to enter and cause the downfall of him and his wife when he should have been the one to crush Satan underneath his heel at the judgment tree of the knowledge of good and evil. Having successfully judged the serpent at the judgment tree, he would then be qualified to partake of the tree of life, and when he does so, Meredith Kline in Kingdom Prologue has this to say:
Having tasted of the tree of life, Adam would have been confirmed in holiness, going from being posse peccare to being non posse peccare. At this point, eternal sabbath rest in glory would be completely assured, yet he would still have to finish his work of populating and taking dominion over all the earth, which he would do with his descendants. Yet, even so, the decisive battle against the serpent had been won. Adam obeyed God and as a result, his probation being ended, his obedience would be imputed to his offspring. They would be born into the world partaking of the benefits and the inaugurated sabbath rest that Adam had won for them. They would have been counted as having obeyed where he had obeyed and the evidence of this is that they would have consequently partook of the reward that he had won, namely, eternal life.
Even so, Jesus Christ, the second Adam, having finished His work in the world, decisively defeated Satan at the cross, crushing his head as Adam should have done (John 12:31-33, Rev. 20:1-3; indeed we already see the beginning of Satan's binding in Jesus' life and ministry as He obeys God in covenantal obedience, bringing in the Kingdom of God cf. Mark 3:27, the temptation accounts, Luke 10:18-19), having been obedient unto death (Phil. 2:8). His work of crushing the head of Satan is then imputed to us so that we are counted as having obeyed where he obeyed even as Adam's descendants would have been counted as having obeyed when Adam (would have) obeyed.
Note too, that His obedience having been imputed to us, we are then called to join in His work of finishing the building of the new sanctuary-temple of the Church through Christ's Spirit (see for instance 2 Cor. 5:17-21, where it explains that having been reconciled to Christ through His imputed righteousness, we are now called to reconcile others to Him through evangelism and so build the church in this way), even as, his obedience having been imputed to them, Adam's descendants were to join him in his work of finishing the building of the sanctuary-temple of Eden.
So when we come to Romans 16:20 we certainly see corporate solidarity that Christians share with Christ in that just as Christ, the ultimate seed of the woman crushed the head of Satan, so too are those seed in Christ said to crush the head of Satan in the future. There is, of course, an already-and-not-yet aspect to the crushing/binding of Satan in that the decisive work was carried out on the cross, but he remains to be permanently defeated at Christ's second coming. So while Romans 16:20 certainly focuses on the "not yet" aspect ("will crush"), it necessarily implies the "already" aspect because our head, Jesus Christ, has already decisively crushed the head of Satan. This means that we are already counted as having done that which Jesus has done. This means that we are counted as having rendered the covenantal obedience that Jesus rendered unto the Father through the crushing of Satan, even as Adam was originally supposed to do in the Covenant of Works.
In short, Romans 16:20 implies imputed righteousness/obedience in that Christ our head, as the obedient last Adam crushed Satan, so we are counted as having done so even as we will do so finally with/in Christ.
Beale also makes a similar argument to mine here in terms of the logic from Ephesians on pages 477-480 of his NTBT; see also pg. 419-422