Generally sharepoint structure is http://server/pages/page1.html
Suppose you need to add a file in root which should access by http://server/page1.html
This can be done by powershell command.
Write-Host “Powershell started…..”
$fileBytes = [system.io.file]::ReadAllBytes(“C:myfolderpage1.html”);
$site = Get-SPSite “http://server”;
$site.RootWeb.Files.Add(“page1.html“, $fileBytes, $true);