Answer
There is another question regarding Noah's ark, how were all the animals able to enter an ark that was only three hundred cubits long. There are so many different types of animals and birds in the world. And if we add to that the size of some of the animals and all the food they need, it is clear that the ark could not accommodate all this. There is a disagreement among the commentators how to answer this question.
According to the Ramban (Genesis 6, 19) and the Keli Yakar (Genesis 6, 15) it was a miracle that a little contained the numerous. In other words the ark had miraculously managed to accommodate all the different types of animals and birds in the world and all the food they needed.
According to the Ibn Ezra (Genesis 6, 16) the question is settled in different ways. Either that the ark was very large, and what is says three hundred cubits, it means cubits according to Noah's size which is much greater than our size, or that there were many arks and the Torah was written here in abbreviated form.
The Radal (Rabbi David Luriya, in his commentary to Pirkei De-Rabbi Eliezer 23, 10) disagrees with these interpretations and explains according to the words of the Pirkei De-Rabbi Eliezer that Noah brought into the ark the 365 main and important types of animals which were originally created. Then they separated and changed into many more types adapting to their land of dwelling, their foods and their occurrences. The Netziv uses the same interpretation in his commentary Ha’amek Davar (Genesis 6, 20).
Based on this we can answer the first question whether there were kangaroos in Noah’s ark. According to the Ramban, the Keli Yakar and the Ibn Ezra, indeed there were kangaroos in the ark, because all the different types of animals in the world were in the ark. According to the Radal and the Netziv that not all the animals entered the ark, but only the basic species, the kangaroo may have been in the ark if it was one of the main species. Or it was not in the ark but later developed from one of the basic animals.
In regard to the second question how did the kangaroos and other animals get to the far reaches of Earth, I did not find any explicit reference to this in the words of our sages. Nevertheless we can say according to the Ramban’s words that the whole issue of the Great Flood was full of miracles such as that there was enough room for all the animals in the ark, and that the animals came to Noah themselves two by two, male and female, and many other miracles. Here also it is likely that the animals miraculously scattered all over the world as G-d's will.
There is another possibility of explaining the matter according to the way of nature, which is the usual way G-d leads the world, that the continents were connected and then separated at a later period. The kangaroo was in the geographic region of Australia when the continents separated. And so did all the other animals each remain in the region where it was during the separation of the continents. Indeed there is a famous theory of geologists called “the Continental drift” which talks about the splitting of the one archaic continent to many continents. And apparently this is indicated in the Torah where it says that in the days of Peleg "the earth was divided" (Genesis 10, 25. This idea was told to me by Rabbi Mordechai Neugroschel).
