XLR to RCA Adapters

Another thought, though I am not the transformer answer guy, I do note that these Jensens (and most?) input transformers of this type want to be loaded by 10K up to 25K for these applications. Your preamp may not like to see this kind of load reflected at a 1:1 ratio -- and don't just go by what someone says "will work": distortions, conventionally measurable or not, tend to increase into lower impedance loads, even with [tube] preamps presenting an output impedance of only several hundred+ ohms. So check this out carefully.

Then, too, I'd guess the BAT's input impedance would need to be modified one way or another -- and IT may not like this change. An advantage of the 4:1 impedance step-down ratio shown for the pro to consumer Isomax is that it takes a 10K impedance across its secondary, and reflects 40K back to the preamp output. All that costs you is some overall available gain in your amplification chain; you probably have a surplus of that on tap as things currently stand.
No, the transformer approach is less than elementary when tube impedances are involved.

Oh, and one more thing... You COULD get a cathodyne (split load) type phase inverter pair made up as an adjunct to the inputs on the BAT. This would get you past the issues I outlined above, at the expense of more circuitry (never a free lunch...). You'd need a power supply for that circuit (not too complicated, in this case), and it would also have the downside of needing a very small value cap at its input so that the circuit can be biased. This sort of thing is also known in a somewhat different context as a bridging adapter. Something in the 6DJ8/6922/7308 range would do. Some feel even lower impedance tubes are better for this (5687, ECC99, D3a triode connected, et.al., down to the circa 800-1200 ohm Rp jobs -- there are various choices for the latter, but their characteristics tend to be all over the place, necessitating tube selection.

Astronaut Norm Thagard designed solid state versions of this in order to bridge FOUR (or was it EIGHT?!) H-K Citation II's for his monster tube system. He published a detailed write-up in 'AudioXpress' (then 'Audio Electronics', I believe), the DIY magazine. It all worked out great, reported Norm.

So, it can be done... Are you sure you want that BAT?

If you are not looking at replacing your preamp with a balanced unit anytime soon, then yes, going with the Jensen transformer would be the best route to take and provide the best results IMHO.
There are advantages of running bal. to bal. (given both circuits are true balanced)but this is not to say that the conversion would not still provide very good results. Regardless of the route you take, you should not have any impedance mismatch as the Rogue has a very low output impedance and most BAT amps have a high input impedance.
I still think the transformer route will still give you a better sound but that is only my personal opinion.

A bad idea. Balanced amps require an inverting and a non-inverting signal. I know trying to do that with an ARC amp results in half the amp output and higher distortion because you are only driving the amp with a non-inverting signal. The inverting side of the signal doesn't exist so that part of the circuit is not being driven. ARC did at one time make a powered device the took an RCA single ended input and gave you a real balanced output. You might want to consider something like that, or a good used balanced output preamp.