Building a strong team must cost money. A team can never be made strong and beautiful without spending money. And yes in this case 'Roma' is not at all interested in spending any money on the team due to which Roma cannot win the title despite being very strong. I think next season Roma need to strengthen the squad to win the title. And they must bring in stars to strengthen this squat. If Roma can bring in stars and strengthen the management then surely they can win the title next season.
But costing a lot of money will not give you guarantee if your team will be as good as you have planned before. Let's take a look at what already done by chelsea. Chelsea has spent a half of billion USD and it was placing at the bottom.
Mourinho has proven even with cheap squads and he was able bringing roma to the european final two times. The main requirement to build a proper team through building the chemistry between the players.
The good team is always having good chemistry no matter how many supers stars in the club. A good club is not always costing a lot of money.
Sometime the club needs to find a good players by buying it from another club but it's not always working properly. Roma didn't have money to sign the new players.
I remember when the owner of roma was giving only less than 8 millions to sign the new players which is very small.
That's why mourintho was not buying expensive players in the winter transfer season.
Usually money can buy you some quality, but as you said you don't have a guarantee that when you buy the 11 most expensive players that you also immediately have the best team in the world. I also think that one big problem is overpaying for quite some time now. I am sure you guys remember some of the numbers that have been paid in the past and you probably thought that the price isn't justified. I have had the feeling a couple of times and even Neymar has never been worth 222 million when he went to PSG. The price is really misleading in many respects but the clubs know that there is so much money in the industry that they can charge it.
Two examples, Kroos cost 25 million when he went to Real Madrid and Modric cost 30 million when he went to Real Madrid. How is that even possible when players like Dembele and Bellingham now cost 150 and 130 million, respectively? Are they 5 times better than Kroos and Modric? I know Dembele is a winger, but there are definitely examples that would also stand the test with a winger.