Blessed John XXIII, in his introductory address, said the following :
The salient point of this Council is not, therefore, a discussion of one article or another of the fundamental doctrine of the Church which has repeatedly been taught by the Fathers and by ancient and modern theologians, and which is presumed to be well known and familiar to all.
For this a Council was not necessary. But from the renewed, serene, and tranquil adherence to all the teaching of the Church in its entirety and preciseness, as it still shines forth in the Acts of the Council of Trent and First Vatican Council, the Christian, Catholic, and apostolic spirit of the whole world expects a step forward toward a doctrinal penetration and a formation of consciousness in faithful and perfect conformity to the authentic doctrine, which, however, should be studied and expounded through the methods of research and through the literary forms of modern thought. The substance of the ancient doctrine of the deposit of faith is one thing, and the way in which it is presented is another. And it is the latter that must be taken into great consideration with patience if necessary, everything being measured in the forms and proportions of a magisterium which is predominantly pastoral in character.
Now, when you wish to adapt something to new conidtions, it is necessary to go back to fundamentals, separating them from the times and places with which it may have become identified. In this sense, yes the mission was to go back to Christian roots in order to adapt the teaching to modern condtions. And this the Council did in spades.
For full text see here.
For full report on Vatican II, see here.