I'm not sure how the rules play out for this, but I want to get combat advantage on #6. Since none of the downstairs party are melee fighters, it would be unwise to try to get them to flank, so can Rogur duck around the corner, do a stealth check, and fire from cover? If not, he'll keep sword in hand and press the attack up close & personal.
Rogur, Round Ten
Option 1: Hide from #6, ranged attack from cover
Move: (Fleeting Ghost) E, N.
* Rogur - Stealth - Hide from #6 *
Minor: Draw sling
Free: Drop sword
Free: Reload crossbow
* Rogur - Sly flourish ranged vs. AC *
* Rogur - Ranged damage *
* Rogur - Sneak Attack damage *
Option 2: Close with #6, melee attack
Move: (Fleeting Ghost) SW
* Rogur - Positioning Strike melee vs. AC *
* Rogur - Melee damage, Slide 2E *