This was my 1st idea:
I'd use a Little Lehle A/B switch to feed my guitar into my Orange Tiny Terror head & my Blackheart combo amp. Then I bought a Hammond aluminum project box, 3 Switchcraft mono jacks, & a 4PDT switch & was going to wire it up so both the Tiny Terror Head & Blackheart amp head went into the box so I could choose which head to pass through to the output. Now the output would feed INTO my Orange cabinet & parallel back out to the Blackheart speaker. This would give me the ability to play EITHER HEAD through basically a 2x12 (one closed-back Orange cab with a V30 & the open-backed Blackheart Celestion).
Cool right? Problem is I can't leave both amps turned on because the one not selected by the 4PDT switch won't see a speaker load & the OT will burn up. My project box switcher would work fine as long as one amp is on at a time. To switch the other one, I'd have to shut down the 1st.
2nd idea:
I decided to buy a Radial Engineering Tonebone Headbone-VT. Not only does it route my guitar signal to both amps, it switches the outputs of either amp as well. I can still daisy-chain the two speakers together in parallel. (Its important that they're the same impedance such as my case 16 & 16-ohms.) When you press the footswitch, the Headbone cross-fades the connections so as one amp output is disconnected from the speakers, it is shunted to a load-resistor while the other one ramps up. Integrity is maintained & everything is optical for no noise switching.
Radial Engineering makes some of the highest quality DI boxes, switchers, & effects available. I can't tout them enough. They make 3 versions of the Headbone, the VT, VS, & SS for 2 tube amps, 1 tube/1 solid-state, & 2 solid-state applications. They run about $240. Mine arrives Friday & I'm quite sure I'll be happy with my new setup as it should be rather versatile.
You can do the same thing to run your TT through your Roadster. The Headbone supports your impedances. Just connect the cables up properly. In my setup, I have 2 16-ohms in parallel which makes for an 8-ohm load. I'd think you could run the TT into your Roadster speakers with the TT's 8-ohm output.
I hope the diagrams layed out above helps. Please let me know what you decide.