If Rosegarden does end up becoming canon, at the very least the show has presented why Ruby would like Oscar back in Volume 6
In Volume 6 words like from Jaune in Volume 5 "you gave us the courage" do comfort Ruby, but also puts her in the position of being responsible for everyone's morale. So later, when things fall apart, Jaune's own words show what that costs. He says bitterly, "Everything we did was for nothing... great plan everyone." If Ruby is the reason the group had courage and hope, then when the plan fails, that failure reflects back on her specifically.
Oscar never speaks to Ruby's guilt directly, but he indirectly changes the emotional environment she's stuck in to something that doesn't single her out as the emotionla anchor.
When the group is falling apart and Jaune is lashing out, Oscar says, "Look, none of this is great, we know. But we're not the bad guys here" and "These past few days, I've been scared of the same things you were... I don't know how much longer I'm going to be me. But I did some thinking, and I do know that I want to do everything I can to help."
And this is why in Volume 7 Ruby is less rushed to answer Oscar compared to Yang:
Yang: (frowning) We're really not gonna tell Ironwood about what happened to Oz? What we learned about Jinn? About Salem?
Ruby: We are. (small sigh) We will.
Oscar: Ruby, hiding things from Ironwood, doesn't that feel like what Ozpin did to us?
While Oscar speaks, Ruby's smile turns into a frown. She turns her eyes away from him in silence.