As I forage around picking up bits & pieces of advise
I,m noticing that getting around Dalmatian Coast
is not that difficult but getting to Romania from
Croatia will need extra effort and I believe that
decision I make will be based on local on the spot
advise

Not that complicated to get to Romania, if you start from Zagreb, although it takes a while. From there the train via Budapest is much faster than via Belgrade and Sofia.

From Dubrovnik there is no good route involving trains. Even if you get a bus from Sarajevo to Belgrade (the train via Banja Luka takes way too long) you still have to go via Sofia with a ridiculously long layover between trains after Sofia. I've been on the Belgrade to Sofia train and can in no way recommend it (unless you want to sit in the sun for hours watching smugglers hiding/recovering contraband).

I'm a big fan of on the ground travel, but for Dubrovnik to Bucharest I'd look into flying. Note that if you insist on going to Belgrade there's also a train from Bar in Montenegro that's supposed to be pretty scenic.

Have made executive decision as follows
D,nik to Zargreb...Zagreb to Budapest (both with a stay)
Finally on to Bucharest & yep by land as I've got heaps
of time
I have to get back to Rome & that I'll do via Vienna (with a stay)
then down to Venice ,Florence & finally Rome
Thanks for your suggestion and yep it ain't difficult
just different

I didn't see anything in the original post about not driving so I couldn't see what you wanted to know since it is an easy trip by car, at least to Bucharest. But, yes, trains and bus are another matter. You do know there are not trains from Dubrovnik to Zagreb, right? If I am wrong, I would _love_ to know it!

There are good ferries, though.

If you really have "heaps of time" that's different - most posters here only have two or three weeks.

With plenty of time you could make a southern loop - Montenegro - Albania - Macedonia - Bulgaria - and up the Black Sea coast into Romania. I did that loop (from Sofia) in reverse as part of a trip in 2011. See: http://www.fodors.com/community/europe/the-b-trip-part-three-western-balkans.cfm

Very good reason not to drive
No licence but thanks for suggestion