OK, so I went and did some data crunching and here is what I found:
(Please note that it may be semi-incomplete. I was going off of archived roster data and while researching I found one or two inconsistancies)
Since 07-08, there have been 41 players that have appeared on the roster in one season and were gone the next. This number excludes graduating seniors. One player was drafted in his junior season, and another was on the roster one year, left for his mission, returned to Weber State and later left the team again without graduating.
Year by year breakdown
2007-08: 16 players on roster, four were seniors, four non-seniors did not return next season
2008-09: 16 players on roster, two were seniors, seven non-seniors did not return next season
2009-10: 14 players on roster, two were seniors, five non-seniors did not return next season
2010-11: 13 players on roster, two were seniors, two non-seniors did not return next season
2011-12: 14 players on roster, two were seniors, four non-seniors did not return next season
2012-13: 15 players on roster, two were seniors, five non-seniors did not return next season
2013-14: 15 players on roster, four were seniors, five non-seniors did not return next season
2014-15: 16 players on roster, one senior, six non-seniors did not return next season
2015-16: 16 players on roster, one senior, four non-seniors did not return next season
17 of the 41 players transferred from another institution to Weber State, where for whatever reason they did not work out and left the team without graduating.
13 of the 41 were at one point or another a walk-on
Here is the list I have compiled. Again, I'm not sure how completely accurate all of this data is as I had to cobble it together from various sources:
Drew Arnold (Transfer to WSU from MSU-Billings)
Danny Johnson (Return from mission, left ISU to go to WSU)
Jamaine Nance (JuCo Transfer)
Juan Pablo Silveira (Not Rahe's signing)
T.J. Benson (Walk-on who later earned scholarship)
Marcus Carson (JuCo Transfer)
Josh Cottle (Return from mission, left UVU to go to WSU)
Terrance Dent (Signed as freshman)
Cody Larson (Walk-on)
Mike Pelo (I couldn't find any information on his situation)
Marco Ramos (JuCo Transfer)
Pablo Coro (Was on the roster one season as a redshirt)
Dee Crandall (Walk-on)
Josh Noble (JuCo Transfer. Looks like he just left the team as he graduated from WSU in 2011)
Franklin Session (JuCo Transfer)
Matt Washington (JuCo Transfer)
Blake Davis (I think he was a Rahe signing, might have been a walk-on)
BJ Porter (Transfer to WSU from Portland)
Mike Brown (Signed as freshman, asked to leave team to pursue other options)
Logan Foster (Walk-on)
Damian Lillard (Drafted by Trail Blazers)
Ryan Van Pelt (Signed as freshman, left on mission, later returned to WSU)
Wayne Bradford (JuCo Transfer, possibly counseled out)
Jordan Rex (JuCo Transfer, possible walk on for his only year at WSU)
Gelaun Wheelwright (Signed as freshman, later departure from team was big enough to warrant a press release from the AD)
Duce Zaid (JuCo Transfer, possibly counseled out)
Brady Borklund (Walk-on)
Josh Fuller (Return from mission, left U of U to go to WSU, possibly counseled out)
Aziz Leeks (Walk-on)
Christian McDonald (Walk-on)
Royce Williams (JuCo Transfer, possibly counseled out)
Jake Bigler (Walk-on)
Jordan Brown (Walk-on)
Chris Golden (JuCo Transfer, possibly counseled out)
Jaelyn Johnson-Coston (JuCo Transfer, possibly counseled out)
Grant Jones (Walk-on)
Ryan Van Pelt (Return from mission, possibly counseled out)
Hayden Hunter (Signed as freshman, later a walk-on)
Jeremiah Jefferson (Signed as freshman)
JC Kennedy (Signed as freshman, later a walk-on)
Juwan Williams (Signed as freshman, left in middle of 16-17 season)
What this says to me, in my opinion, is most of Rahe's swings and misses feel like they are transfers from other institutions, that were probably brought on more as a short term fix than with plans for playing a major part in the future. I'm not an expert by any stretch of the imagination and I've only been following the team since 2011, so I defer to the opinions of more experienced fans on this board.