"We will try to play with our best team", said the 64-year-old Rohr, from Germany.
It was also the first time England goalkeeper Jordan Pickford had conceded since the World Cup qualifier against Slovakia in September, but the hosts managed to keep their opponents at bay thereafter.
England and Nigeria have faced each other twice: the two teams drew 0-0 at the 2002 World Cup, while the Three Lions won a friendly 1-0 back in 1994.
Pickford is only 24 and relatively inexperienced, but he will have gained confidence from an error-free performance in the win.
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The game began positively for England as Gary Cahill headed home from a Kieran Trippier corner with less than seven minutes on the clock. "After 10 minutes we got to grips with their shape and managed the game well".
"I think first and foremost he has conducted himself fantastically well this week, he has managed that situation very well". So credit to him. He created quite a few chances.
Southgate will no doubt be pleased with the win, but concerned at a sloppy start to the second-half by his charges.
England's Group G campaign in Russian Federation begins against Tunisia on June 18, but first they have a final friendly with Costa Rica at Elland Road on Thursday.
"As I always say, a team's first game will determine how far it can go at a tournament".
"I think the pace in the team, you can feel it, and that is why we had some problems in the first half."In the second half we corrected some mistakes and played a lot better".