God didn't leave any escape clauses. He made it quite clear.
Matthew 7:21 Not every one that saith to me, Lord, Lord, shall enter into the kingdom of heaven: but he that doth the will of my Father who is in heaven, he shall enter into the kingdom of heaven."
Matthew 25:31 And when the Son of man shall come in his majesty, and all the angels with him, then shall he sit upon the seat of his majesty.  And all nations shall be gathered together before him, and he shall separate them one from another, as the shepherd separateth the sheep from the goats:  And he shall set the sheep on his right hand, but the goats on his left.  Then shall the king say to them that shall be on his right hand: Come, ye blessed of my Father, possess you the kingdom prepared for you from the foundation of the world.  For I was hungry, and you gave me to eat; I was thirsty, and you gave me to drink; I was a stranger, and you took me in:
 Naked, and you covered me: sick, and you visited me: I was in prison, and you came to me.  Then shall the just answer him, saying: Lord, when did we see thee hungry, and fed thee; thirsty, and gave thee drink?  And when did we see thee a stranger, and took thee in? or naked, and covered thee?  Or when did we see thee sick or in prison, and came to thee?  And the king answering, shall say to them: Amen I say to you, as long as you did it to one of these my least brethren, you did it to me.
 Then he shall say to them also that shall be on his left hand: Depart from me, you cursed, into everlasting fire which was prepared for the devil and his angels.  For I was hungry, and you gave me not to eat: I was thirsty, and you gave me not to drink.  I was a stranger, and you took me not in: naked, and you covered me not: sick and in prison, and you did not visit me.  Then they also shall answer him, saying: Lord, when did we see thee hungry, or thirsty, or a stranger, or naked, or sick, or in prison, and did not minister to thee?  Then he shall answer them, saying: Amen I say to you, as long as you did it not to one of these least, neither did you do it to me.
 And these shall go into everlasting punishment: but the just, into life everlasting.
Romans 2:13 For not the hearers of the law are just before God, but the doers of the law shall be justified.  For when the Gentiles, who have not the law, do by nature those things that are of the law; these having not the law are a law to themselves:  Who shew the work of the law written in their hearts, their conscience bearing witness to them, and their thoughts between themselves accusing, or also defending one another,
Mt. 7:21 is immediately followed by the following verses:
22 Many will say to Me in that day, ‘Lord, Lord, have we not prophesied in Your name, cast out demons in Your name, and done many wonders in Your name?’ 23 And then I will declare to them, ‘I never knew you; depart from Me, you who practice lawlessness!’
Ask yourself this: Is not prophesying in Jesus' name, casting out demons in Jesus's name, and doing many wonders in Jesus' name not among the will of the Father? While Mt. 7:21 is clear that only those who calls on to Jesus as Lord and does the will of the Father will be those who will enter the Kingdom of God, one must ask oneself, what will of God is Jesus talking about? If not things such as prophesying, casting out demons, and doing many wonders, in Jesus' name, what will of God is Jesus referring to? I'm quite sure that many think of the commandments found in the Law, especially the ten commandments. And so, I am not surprised that you cited Romans 2:13 which speaks of doers of the law. And having cited Mt.25:31-46, are you saying that the will of the Father Jesus was referring to in Mt.7:21 are such works as those mentioned that the sheep had done?
Now, is that the will of the Father that Jesus is referring to in Mt.7:21? Does Jesus really speak of these works, or is there more to it than the works themselves, that is the will of the Father which Jesus is meaning to teach?
I have made my point I guess, so I'll leave that question for you to ponder upon.
Also with regards Mt.25:31-46, it speaks about Christ, when He comes and sit on the throne of His glory, as will separate the nations one from another. He is figured to be as a shepherd who divides HIS
sheep from the goats (Mt. 25:32). Now, the sheep will inherit the kingdom, while the goats will go into the everlasting fire. It brings to mind, what Jesus told the apostles in John 10, He likens Himself in the figure of a Shepherd who owns the sheep (HIS
sheep that is). And Jesus goes on to say regarding this that when He, the good Shepherd, brings out His own sheep, He goes before them, and the sheep follow Him, for they know His voice. And He said in John 10, 14 "I am the good shepherd; and I know My sheep, and am known by My own
. 15 As the Father knows Me, even so I know the Father; and I lay down My life for the sheep.
Who are the Good Shepherd's (Jesus') sheep, HIS sheep? They are those who belong to Him as being His own. They are those whom Jesus leads. They are those who know His voice and follow Him. They are those whom He knew and is known by them. And finally, but certainly the first, they are those whom Jesus will lay down His life for.
Finally, with regards Romans 2:13, I will have to cite a few verses to point out the truth concerning the matter of the law:
Galatians 3:11 But that no one is justified by the law in the sight of God
is evident, for “the just shall live by faith.”
Galatians 3:24 Therefore the law was our tutor to bring us to Christ
that we might be justified by faith.
James 2:10 For whoever shall keep the whole law
, and yet stumble in one point, he is guilty of all