In Act 1, Scene 4 from Macbeth, when Macbeth speaks of the proper role of the king and subject in this scene, does he truly believe in what he says, considering the fact that moments later he thinks of murdering the king?
Prior to the meeting with the witches, Macbeth had been a loyal servant to the king. However, at this point, the possibility of becoming king is on his mind. So, when Macbeth utters those lines, he is just acting the part of the loyal subject. He does not want to arouse suspicions, which he divulges in an aside:
Let not light see my black and deep desires:
The eye wink at the hand; yet let that be
Which the eye fears, when it is done, to see. (I.iv.58-60)
So, the answer to your question, is no, he is no longer thinking of himself as the loyal servant of the king. However, in foreseeing himself in the role of king, he does expect his future subjects to be loyal. This becomes clear as the play unfolds. Macbeth will kill anyone whom he feels is a threat to his reign. He believes in the meaning behind those lines, but only as it applies to himself as king.