Following PS cmdlet will export the RBAC role assigned to users, groups of your AAD as well as the group members details to a csv file. Make changes in the variables as per your AAD

$subscriptions = Get-AzSubscription -SubscriptionID "sub id"
$allRoleAssignments = @()
Write-Host "Fetching role assignments for subscription: $($subscription.Name)" -ForegroundColor Cyan
# Set the context to the current subscription
Set-AzContext -SubscriptionId $subscriptions.Id
# Get role assignments for the current subscription
$roleAssignments = Get-AzRoleAssignment | ForEach-Object {
    # Initialize an array for group members
    $groupMembers = @()
    # Initialize the group display name
    $groupDisplayName = $null
    # Debug: Output PrincipalId and PrincipalType to verify if it is a Group
    Write-Host "Checking role assignment for PrincipalType: $($_.PrincipalType), ObjectId: $($_.ObjectId)" -ForegroundColor Yellow
    # Check if the role assignment is tied to a group
    if ($_.ObjectType -eq "Group") {
        try {
            # Get the group display name by using the group ObjectId (PrincipalId)
            $groupId = $_.ObjectId
            Write-Host "Fetching group with ObjectId (PrincipalId): $PrincipalId" -ForegroundColor Yellow       
            # Get the group details using ObjectId (PrincipalId)
            $group = Get-AzADGroup -ObjectId $groupId
            $groupDisplayName = $group.DisplayName
            # Debug: Confirm the group display name
            Write-Host "Group DisplayName: $groupDisplayName" -ForegroundColor Green
            # Get members of the group
            $members = Get-AzADGroupMember -GroupObjectId $groupId
            if ($members) {
                # Add each member's UserPrincipalName to the groupMembers array
                $groupMembers = $members | ForEach-Object { $_.UserPrincipalName }
            } else {
                Write-Host "No members found for group: $groupDisplayName" -ForegroundColor Yellow
            }
        } catch {
            Write-Host "Error fetching group members for group ID $($_.ObjectId): $_" -ForegroundColor Red
        }
    }
    # Create a custom object for role assignment with group display name and group members
    [PSCustomObject]@{
        SubscriptionName   = $subscriptions.Name
        SubscriptionId     = $subscriptions.Id
        PrincipalName      = $_.SignInName
        PrincipalType      = $_.PrincipalType
        RoleDefinitionName = $_.RoleDefinitionName
        Scope              = $_.Scope
        DisplayName        = if ($_.ObjectType -eq "Group") { $groupDisplayName } else { $_.DisplayName }
        GroupMembers       = $groupMembers -join ","  # Concatenate group members as a string
    } | Export-CSV "C:\azure\RoleAssignmentDetails.csv" -NoTypeInformation -Append
}