Lukaku has become very ferocious lately and this cannot be separated from his goal contributions for Rome and Belgium. On average, he can always score 1 goal and apart from that, this is good progress for him amidst the issue of declining performance last season. Currently Lukaku has become an important player for the teams he plays for everywhere and that means a lot to him. The competition in the top 4 is still quite difficult for Roma and maybe they have to add more players in the winter so they can be more consistent in maximizing results in every match.
Having a run like he had in the last game with Belgium when he scored 4 goals is of course amazing, but calculating the average goal per game ratio can sometimes be a misleading tool. If a player scores 4 goals in one game and then no goal in three games, I think every team would wish for the striker to instead score 1 goal per game more reliably. He has had some impressive games, but consistency isn't so much about maths, it is about how often he is the one to decide the game with his goals. That is what counts and Roma could need more decisive goals as they are stuck in the table.