ENGLEWOOD (AP) – John Elway is scrambling again.     The general manager of the Super Bowl champions has a huge hole to fill with Brock Osweiler bolting to the Houston Texans 48 hours after Peyton Manning’s retirement.   That leaves Trevor Siemian as the only quarterback on the Denver Broncos roster. The second-year pro from Northwestern has taken just one NFL snap, a kneel-down at that.   Elway could turn to free agents such as Robert Griffin III or Ryan Fitzpatrick or he could pursue a trade – Colin Kaepernick, anyone? He’ll almost certainly select a quarterback in next month’s draft, too.   Osweiler made $660,000 last year and Denver offered him about $16 million a year. ESPN reported Osweiler’s four-year deal with the Texans is worth $18 million annually.