I just got a Roland Octa capture and am getting great sound through it. I have finally figured out how to separate the stereo channels into individual channels. I want to use this to primarily capture individual tracks of my band both live and in 'Studio'. The band is gospel bluegrass/jug band. Some specific questions.

Is it best to use the audio output from the interface to drive the monitors and just let the digital go into Sonar dry.

Can you just turn turn record on and let it go for sn entire session?

How do you avoid cross talk between tracks when recording live?

Are there ways to simplify everything until I gain more experience?

Welcome to the world of Sonar and recording.
The learning curve is notoriously steep at first, and you have certainly jumped into the deep end of the pool.
I can only imagine the initial experience has inspired some very un-gospel verbage.
 
These are all valid questions, and you may want to ask them in the Techniques forum. You'll get better exposure, and there are some very knowledgeable folks that hang around there.
 
You can let Sonar record continuously. Be sure to turn off all power management options in windows beforehand.
There used to be a 2GB limit on file size, but that may no longer apply. It may be easier in the long run to record smaller segments as you go.
 
As for simplifying everything, try some smaller projects to get your legs under you.
You'll want to build a dog house or two before you build the Taj Mahal.
 

Wise words from Mr Bob, 
 
Yes your studio monitors are driven from the interfaces monitor output so you can utilize the direct monitoring without experiencing system latency when overdubbing. By digital I assume you mean the USB output of your 8 channels, yes those are what you will record in Sonar. 
 
You Can record a whole session if you wish to focus on your playing and not fuss between songs. What I do is create a template that is for the session. I then open and do "save as" for each song if I know or just number in sequence up to say 30. So I have 30 blank named projects ready to go before hand. 
On the day of the session I open them all and minimize to the bottom. It now only takes a few seconds to have a blank template open and armed for recording. You can bang off the songs and when there's a short break start saving them. 
 
Cross talk is a huge topic and best dealt with as Bob has said as a separate thread in the other forum. I will relate what I do. 
We are focusing on the drums for the first sessions, the only live mikes in the room are on the drums
The Bass and guitar are DI's to the interface and the keyboards use MIDI. Each player has a monitoring rig via a few small mixing boards and use headphones. The vocals are just scratch and they are isolated as best as possible as far from the drum mikes as possible, we use office dividers.  
 
Keeping it simple is a great idea but a little harder to do with a live band. 
You might want to record a few simple songs by yourself first. 
Good luck and have fun. Your studio time is free now... 
 
 

Thanks for the advice. I have to laugh at the last comment about studio time being free. Miss J (the soprano half) probably would not agree if she ever saw the Sweetwater bills. I probably will have many more questions after I spend time recording some solo sessions this weekend.

Bass is an attitude not a part.

Ha ha, Guess I should rephrase that to "Studio time is now free but not the actual studio" 
 
But most musical gear will serve you for many years if you buy wisely. Most of my stuff is over 25 or 30 years old. Only this stupid computer stuff is disposable. I have definatly spent more on outdated software than microphones and cables.