JAY Z’S ROC NATION SPORTS UNDER INVESTIGATION FOR GENO SMITH   TMZ REPORTS  Jay-Z‘s foray into sports management has already hit a snag — the NFL is investigating whether the rap superstar violated league rules involving the recruitment New York Jets draft pick Geno Smith. JAY Z LOSES OWNERSHIP OF BROOKLYN NETS Jigga’s Roc Nation Sports signed Smith earlier this week and a photo of Smith with Jay-Z was posted to Instagram prior to the announcement. The problem is … league rules mandate that only NFLPA-certified agents may be involved in the recruitment of clients. JAY Z EXECUTIVE PRODUCER OF THE GREAT GATSBY Also complicating matters … Smith’s adviser, John Thornton,…