I have broken the arm of Pharaoh - Perhaps this may refer to his defeat by Nebuchadnezzar, when he was coming with the Egyptian army to succor Jerusalem.
Fourth prophecy against Egypt spoken three months before the capture of Jerusalem Ezekiel 26:1, and three months after the prophecy of Ezekiel 29:1. Meantime, Pharaoh-Hophra‘s attempt on Jerusalem had been foiled, and the Egyptians driven back into their own country (Jeremiah 37:5 note).
Ezekiel 30:21
I have broken - Especially by the defeat at Carchemish.
A roller - Or, a bandage.
Ezekiel 30:22
The strong - Such power as Egypt yet retained at home and abroad.
That which was broken - The power which Egypt aimed at ineffectually, the conquest of Palestine and Syria.