Peter Roh (born at Conthey (Gunthis) in the canton of Valais, Switzerland, 14 August 1811; d. at Bonn, Germany, 17 May 1872) was a Swiss Jesuit preacher.
While there, he resolved to enter the Society of Jesus (1829); strange to say the external means of bringing him to this decision was the reading of Pascal's pamphlet Monita Secreta.
These labors were interrupted by the breaking out of the Swiss Sonderbund war, during which he was military chaplain; but after its end he was obliged to flee into Piedmont, from there to Linz and to Gries.
When the Catholic missions for the common people were opened in Germany in 1850, his real labors began; as he said himself, "Praise God, I now come into my element."
In his pamphlet "Das alte Lied: der Zweck heiligt die Mittel, im Texte verbessert und auf neue Melodie gesetzt", he declared he would give a thousand florins to the person who could show to the faculty of law of Bonn or Heidelberg a book written by a Jesuit which taught the principle that the end justifies the means.