The youngsters will stay with the Conference North club, who current sit one place above the relegation zone, until mid-March.
They are available for selection when Stalybridge face Brackley on Saturday.
Preston manager Simon Grayson said: "This is an excellent opportunity for both Ryan and Jack to go out and experience what it is like to fight for three points every week.
"As a club, we think very highly of them both and this experience will help their development no end.
"Stalybridge are a full-time club playing at a decent level and I'm sure the players will enjoy the chance to play regular first team football."
Croasdale, 19, was on loan at Tamworth earlier this season but this will be 17-year-old Ryan's first taste of competitive football.
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