Cole Kmet received extensive job assurances from both Ben Johnson and Ryan Poles throughout last week’s draft.   That's fine for print and broadcast to calm down fans, and good probably for everything up to and including training camp or later.   However, during virtually every season, NFL teams will get through preparations for the coming season and discover the talent they've brought in can do the job sufficiently or even better than higher-paid veterans. Then trades get made. If preseason/training camp doesn't effectively convince them to trade or keep a player, the first half of the season can. Then the trade occurs before the trading deadline, at the end of October or in early November.  Ben Johnson says “no block, no rock.” Sam Roush fits that perfectly.…