Ascension of the Lord: Theosis in the Roman Church?

From the first sermon on the Ascension of Pope St. Leo the Great:

"After the blessed and glorious Resurrection of our Lord Jesus Christ, wherein the Divine Power raised up in three days the true Temple of God Which the iniquity of the Jews had destroyed, God was pleased to ordain, by His Most Sacred Will, and in His Providence for our instruction and the profit of our souls, a season of forty days which season, dearly beloved brethren, doth end on this day. During that season the bodily Presence of the Lord still lingered on earth, that the reality of the fact of His having risen again from the dead might be armed with all needful proofs. The death of Christ had troubled the hearts of many of His disciples their thoughts were sad when they remembered His agony upon the Cross, His giving up of the Ghost, and the laying in the grave of His lifeless Body, and a sort of hesitation had begun to weigh on them.

"Hence the most blessed Apostles and all the disciples, who had been fearful at the finishing on the Cross, and doubtful of the trustworthiness of the rising again, were so strengthened by the clear demonstration of the fact, that, when they saw the Lord going up into the height of heaven, they sorrowed not, nay they were even filled with great joy And, in all verity, it was a great an unspeakable cause for joy to see the Manhood, in the presence of that the multitude of believers, exalted above all creatures even heavenly, rising above the ranks of the angelic armies and speeding Its glorious way where the most noble of the Archangels lie far behind, to rest no lower than that place where high above all principality and power, It taketh Its seat at the right hand of the Eternal Father, Sharer of His throne, and Partaker of His glory, and still of the very man's nature which the Son hath taken upon Him.

"Therefore, dearly beloved brethren, let us also rejoice with worthy joy, for the Ascension of Christ is exaltation for us, and whither the glory of the Head of the Church is passed in, thither is the hope of the body of the Church called on to follow. Let us rejoice with exceeding great joy, and give God glad thanks. This day is not only the possession of Paradise made sure unto us, but in the Person of our Head we are actually begun to enter into the heavenly mansions above. Through the unspeakable goodness of Christ we have gained more than ever we lost by the envy of the devil. We, whom our venomous enemy thrust from our first happy home, we, being made of one body with the Son of God, have by Him been given a place at the right hand of the Father with Whom He liveth and reigneth, in the unity of the Holy Ghost, one God, world without end. Amen."