Roma will win against Lecce it's almost certain, even if Lecce plays at home it will be a piece of cake for them to beat them, let's remember that Roma is very well placed in the standings and with a coach like Ranieri they can really make the difference in this final part of the championship
A better ranking in the standings does not guarantee a team can always win when facing a team in a lower ranking like Lecce, because a team like Lecce can also make a good performance that can cause the final result to be beyond many people's expectations. Although before the match started almost everyone might have tipped Roma as the winner in the match, but unexpected results are always possible to happen in the match.
This is true, it doesn't guarantee anything at all, and it's a risk and we should not be considering this to be very important piece of the part, because you can't make this work if you just bet on the better teams and then hope that the rest just happens easily. That won't be how this works at all, if it was that simple, then we would all just bet on the team with better ranking, and then we would all be just making money, that's just how it is.
So if we could end up with something that will take a while for it to be a real bet. This is why, if we could just focus on who will win, without looking at the standings, but just looking at the difference between the team quality, then we would have a higher chance of winning.