Senator Scott Brown got the pretty picture every politician covets as he read to a gaggle of cute kids at Horizons for Homeless Children in Roxbury. But there was a serious message behind it. “We’re depending on you,’’ chief development officer Meryl Sheriden told Brown. However, the Bay State’s Republican senator was noncommittal when staff members reminded him that their program would be affected by the automatic spending cuts that federal agencies face after failure by a bipartisan super committee. The children spend days at the center and nights at shelters and Brown seemed touched by his interaction with them. But he was noncommittal when staff members reminded him that their program would be affected by the automatic spending cuts that federal agencies face after failure by a bipartisan super committee to identify $1.2 trillion to reduce the deficit.