Gilgameshuu said:Let's first figure out what Roswaal's goal is, at least pieces of it. We know in Season 1 that he wants to kill the Dragon Volcanica, a being that supposedly formed a contract with the Royal Family to protect Lugnica, and in this episode, Ram mentions that Roswaal's wishes will be granted once Emilia takes the throne, if we connect the dots, we can hypothesize that Emilia taking the throne is just one step to achieve his goals, after that we can guess that since Emilia is the ruler, that will make it so that it's possible for Roswaal, as her backer to get closer to the Dragon and kill it, why or what happens after that we don't know, but it must be something related to Echidna, that's for sure.
1) Let's start with the mansion, what was the point in Roswaal sending assassins to the mansion again? they will kill everyone in the mansion so Roswaal know this will force Subaru to stay in the forest living in a loop because Subaru won't let that happen and he will keep re-doing it to save everyone and thus, Roswaal would stay in a loop as well and he should know this.
Roswaal wants to strengthen Subaru's resolve by choosing to protect one precious thing, and that one precious thing alone while sacrificing everything else, for Subaru, that one precious thing is Emilia.
This is the major miscalculation in Roswaal's part though, and that's Rem's whole existence, since she was erased from everyone's memory except for Subaru, and thus history and time re-adjusts itself as if she never existed in the first place, maybe Rem isn't present in Roswaal's tome? Even if she did, he would have no memories of her so he wouldn't think of her as much, and we know Rem is very important to Subaru, that's also partly the reason why he didn't want to just choose Emilia since that would mean sacrificing Rem.
Basically, what Roswaal wants is to manipulate Subaru, forcing him to choose Emilia over everything else, and doing the trials in her place, this will leave a deep scar into him that will haunt him forever, making him a mentally weaker person, and the same goes for Emilia, she won't be able to face and overcome her past and regrets, making her mentally unstable like what happened in S2E11. Once the two of them become like this, it will be easier for Roswaal to manipulate the both of them to achieve his goals.
2) The thing Roswaal is trying to do will require a lot of mana and hence it will attract the bunnies to the forest and thus, killing everyone in the process including him, Roswaal should know something like this will happen (it should be in his book). This will force Roswaal to live in a loop again.
Regardless of what will happen, Roswaal relies on the Tome, as it's a pathway to achieve, we're not even sure if the rabbits will kill everyone maybe the Tome has some instruction on how to exterminate the rabbits.
3) It doesn't make sense for Roswaal to revive Echidna the way he's doing things because the way he's doing it will have everyone killed and thus, living in a loop or will force Subaru to keep living in a loop till he succeeds.
Same as my last sentence, we don't know if it will actually kill everyone. Since the Tome is a guide to Roswaal's future, there must be a way written there on how to defeat the rabbits, if not then that's contradicting the Tome's purpose.
4) What is the point in Roswaal having Subaru to help Emilia again? Roswaal wants Emilia to fail but if Subaru helps Emilia then she will most likely succeed, Roswaal should know that this will require a lot of "redo" from Subaru's part and he will succeed sooner or later, otherwise they will keep living in a loop forever and I'm sure this is not what Roswaal wants so... what was the point in all of his actions again?
I'll reiterate my answer in your first question, Roswaal wants to push Subaru into a corner so that he chooses to prioritize Emilia over everything else, and that also involves taking the trials instead of Emilia, leaving both of them mentally weaker and easier to manipulate for his goals.