Something along the lines of
Dim i As Long
Dim LASTROW As Long
LASTROW = Cells(Rows.Count, 1).End(xlUp).Row
For i = LASTROW To 1 Step -1
If InStr(Range("A" & i).Value, "R") Then
Range("A" & i).EntireRow.Insert Shift:=xlDown
Range("A" & i).Value = "R"
Range("A" & i).Offset(0, 1).Value = 349273
End If
Next i