This intrigues me :P
This might be doable with a trainer I think! I can do this with Cheat Engine no problem.
Pick up one, search (Double: 1), then drop it and search (Double: 0).
Repeat for second grimoire and narrow down the value for the grimoire and set to "7".
Finish mission without picking up any dice and/or tomes and get the highest tier roll item.
I think this can be incorporated into the trainer, maybe even add values for how many grimoires you want.
*Note, grimoire count cannot exceed 7 as the maximum rollable dice combined is limited to 7 rolls.
[Edited by DglShadow, 10/26/2015 5:19:54 AM]
[Edited by chevalier7, 10/26/2015 8:55:22 AM]
This is exact same thing happening to me.
[Edited by PWizard, 10/26/2015 9:46:52 AM]