This comes from the PYSA Registrar's manual, page 9:  http://www.portlandyouthsoccer.com/doclib/Registrar%20Manual%20rev3%20(2).pdf 

Check the registrar web page for updates: http://www.portlandyouthsoccer.com/home.php?layout=535216

Roster Sizes/Roster Recommendations

 *(K) U5/6 In house programs within your club
 *(1 st) U7 Roster Size Recommendation = 10 3v3; Max Roster = 12
 *(2 nd ) U8 Roster Size Recommendation = 12 4v4; Max Roster = 14
 *(3 rd ) U9 Roster Size Recommendation = 12 7v7; Max Roster = 14
 *(4 th ) U10 Roster Size Recommendation = 12 7v7; Max Roster = 14
 *(5 th ) U11 Roster Size Recommendation = 14 9v9; Max Roster = 18
 *(6 th ) U12 Roster Size Recommendation = 14 9v9; Max Roster = 18
 *(7 th ) U13 Roster Size Recommendation = 16 11v11; Max Roster = 18
 *(8 th ) U14 Roster Size Recommendation = 16 11v11; Max Roster = 18
 *(9 th & above) HS Roster Size Recommendation = 18 11v11; Max Roster = 22