Big Picture Thoughts:
Roman used to use Cahill Field at 29th and Allegheny. Stands were well back from the field but could accommodate a crowd of 7-8 thousand. Don't know who owned it (the Archdiocese?) but I assume it was sold a long, long time ago. Didn't have parking and wasn't close enough to a subway station.
For both Roman and the Prep having a really good football team has limited value for the school community (including the alumni) if it's really hard for nearly all of them to get to games (as it is when they're played in Norristown) and they're not available via streaming. Bob Long does a nice job with LaSalle games. Not sure why neither Roman nor SJP has done something similar.
Catholic league teams used to play occasionally at Villanova. No idea why that hasn't happened in about 10 years. There are obvious advantages to the site. I assume nothing is suitable at LaSalle, not even the old McCarthy "Stadium". But if there is some workable space there, there would be advantages to the site. My impression was that Franklin Field worked well for the SJP-LaSalle games in recent years. Surely the PCL could negotiate a workable date with Penn--maybe for SJP-Roman and Roman-LaSalle too--as long as the price isn't too high.
I've often wondered if the South Philly supersite (12th and Bigler, just off the Expressway) wouldn't be really good for SJP and maybe Roman too--not too far from the subway and certainly convenient for people coming from Jersey, the Northeast (via 95) and much of Delco (Parking isn't great but not impossible.) What the site needs is an upgrade to the turf, the stands, etc. But it's big enough.
Finally, we all know the Archdiocese has a lot of properties--e.g. the Hallahan site and numerous ones where a church (often with adjoining former school/rectory/convent properties--it is no longer using for their original purposes. I'd bet more than one has real potential as a football (maybe track too) site with enough room to seat at least a couple of thousand people. It might not be so close to the subway and parking will almost always be a problem, but it would certainly be better than Widener, Norristown, the Germantown site Roman has sometimes used, and even P-W, which had its own problems for SJP.