Null autocorrelation function and stationary
If E[X(t)] is constant and RX(t+τ,t)=0 can I say the process is WSS?
Can I say RX(t+τ,t)=0=RX(τ) and therefore is WSS?

Two times the same question.
It fulfills the definition (as you noticed yourself), so why even ask? yes.

What does RX(t+τ,t)=0 mean?

It means the process is uncorrelated ($R_X(\tau \ne 0)=0$), but also that its variance is 0 ($R_X(0) = \sigma_X^2 =0$). There's only one process that fulfills that:
$X(t) = 0$
not a really exciting process, is it?