Firstly, you say "the spell strikes the foe in the flank". Spells don't flank (unless it's something like flame blade, and that only flanks because it acts as a melee weapon).
Here's a couple of suggestions.
Start with the cleric spell Imbue with Spell Ability. With an arcane version of this spell the rogue could cast the wizard's ray. Fiddle with the parameters until it seems right. Be careful not to break the action economy.
Invent a metamagic feat that allows the wizard to designate someone else as the toucher using the same rules that allow familiars to be designated the toucher.
Tere's a spell in some paizo campaign world book that enables this as a spell.
Step 1: cast spell on creature (creature may try to save or just take it).
Step 2: cast spell and make it originate from previous target.
(Note. Only works with cone, line or burst area spells)
There also probably some 3.5 material you can use.
Custom insta feat invented on the spot:
[Metamagic]Remote spell:
When you cast a Remote spell choose a willing subject within 30 ft.
The spell treats the chosen creature as it's point of origin for all purposes.
A touch spell so cast must be held and delivered by the creature on its own round.
Any effects relating to "you" apply to the creature instead. (A remote shield for example affects the target creature instead of yourself)
When choosing targets or determining area, do so from the point of view of the chosen creature, you still rely on your own senses.
A remote spell takes up a spell slot 2 levels higher then usual.
Spells need line of sight or line of effect. Although sometimes line of sight is optional. If a spell changes where line of effect originates then line of effect woukd be figured out from there.
Here's the kicker though a lot of the spells that let you see other places need to specifically give you line of sight or effect.
But in your example above if the wizard and rogue had some shared amulet item if it allowed the wizard ro cast from the rogue as if he lad line of effect then the spell woukd originste from the rogues square. But without line of sight the wizard is blind or canot target enemies at all.
I believe there is an amulet that does this...that allows a caster with the companion amulet to transfer a spell to the other wearer that they may fire off using the original caster's stats for the variables of the spell.
Tere's a spell in some paizo campaign world book that enables this as a spell.
Step 1: cast spell on creature (creature may try to save or just take it).
Step 2: cast spell and make it originate from previous target.(Note. Only works with cone, line or burst area spells)
There also probably some 3.5 material you can use.
Custom insta feat invented on the spot:
[Metamagic]Remote spell:
When you cast a Remote spell choose a willing subject within 30 ft.The spell treats the chosen creature as it's point of origin for all purposes.
A touch spell so cast must be held and delivered by the creature on its own round.
Any effects relating to "you" apply to the creature instead. (A remote shield for example affects the target creature instead of yourself)
When choosing targets or determining area, do so from the point of view of the chosen creature, you still rely on your own senses.
A remote spell takes up a spell slot 2 levels higher then usual.
The spell is Eldritch Conduit and Greater Eldritch Conduit.
The feat Split Hex used in conjuction with a witch's Scar Hex lets you pull off a similar effect with Heses.
/cevah
There's also Project Image. Much higher level but it's the classic wizard decoy.