So, I have a lot of issues with rogue.
It gets spell buffs, but the rogue spells can't really share damage types unless you go fire, which is at divinity 18. (Other than fissure spikes)
Grenade can't be converted to spell (so you can't combine with fissure)
Grenade Payload doesn't seem to honor weapon damage convert at all. It seems to convert weapon damage already to fire, so it ignores the sustained conversions.
Vitality damage is a possible synergy with warfare, but it's at divinity 18 also.
There are no conversions to poison in other mastery, so you can't have poison be a shared spell damage type.
The only AOE spell vitality (Vanish/Flicker Doom) is also at level 18, and it's on a CD
What I would recommend
Move the fire and vitality conversions down to lvl 6 divinity, and move the nimble defense up instead.
Give the grenade a spell conversion to piercing or poison, so it can use the spell conversions.
Give Preparation a vitality bonus somewhere.
Make a default shadow ability in Rogue that does spell damage.
Either reduce the cost of grenade or increase ailment chance. Compared to call lightning, which has the same cost, the damage is significantly less.