As others have said, I think this would probably kick the can further down the road; the Turkmen raids into Asia Minor would continue, and at some point, the Seljuks would probably turn on the Byzantines - they were still considered to be one of, if not the preeminent power in the Middle East at the time, and they were the traditional enemy of the caliphs. With the Byzantine army still around, and the consequent threat of action against his rear, I think Alp Arslan would try to end the war with the Fatimids more quickly - perhaps not advancing beyond Aleppo and Damascus, and prepare for confrontation with the Byzantines.
However, the political situation in Constantinople would still be rather problematic. Relations between Romanos and the Doukai had hit a new low in 1070, when he had declared his sons from Eudokia as co-emperors, as it was becoming increasingly clear that he was most likely planning to replace the Doukai with a dynasty of his own - he had been marginalising Eudokia from government for some time, and the banishment of John Doukas was a further sign, plus there was bad blood between the two sides since the days of Constantine X, so I think that the fears of John Doukas and his allies were justified. If Romanos has managed to complete the operation in the East without much trouble and perhaps no sign of the enemy, he might decide to return to the capital. I am not sure how the Doukai would react to this: on the one hand, the possibility of further unfavourable dynastic settlements was very real, on the other, there was little they could do about it yet. However, were the threat of overthrow to be seen as dangerous enough, I think they would get into action: by accusing him of breaking the terms and oaths from his marriage with Eudokia about protecting the interests of the dynasty, they could launch a coup at the capital and thus declare Romanos unfit of the imperial title, while in the army itself, Andronikos and others could rouse trouble with the mercenaries.
Best case scenario, Romanos is caught off guard and imprisoned, his allies are neutralised for the most part, and the Doukai manage to consolidate their control in the short term at least; they would still have to deal with remaining loyalists of Romanos, the problems of the Seljuks and raids in the Balkans, the need for reforms (mainly to find funds for defence), and the rivalries with other aristocratic families, particularly the Komnenoi, but with Anatolia mostly stable and the field army mostly intact, they would have a good starting point. At some point, John Doukas would probably remove Eudokia Makrembolitissa from power, leaving only him and Michael; I am not sure how relations between the two would develop, because from the record of his reign, I think we can say he did have plans of or aspired to implement large scale reforms to restore imperial finances and the administration, as well as contain the powers of the aristocracy, which could bring him in conflict with his aristocratic uncle.
Worst case scenario, the army mutiny is suppressed, Romanos marches on Constantinople, a full civil war breaks out, the Seljuks press their advantage by raiding eastern Anatolia and are perhaps introduced in the conflict as the Doukai could think of using them to distract and weaken Romanos' forces while they are raising an army of their own. We get a rerun of the OTL 1070s to a large extent, perhaps a more limited version with fewer usurpers, but still messy.
The guy was likely betrayed by the Doukas family in the battle itself and Romanos himself was captured by the Seljuks in the battle. What exactly was Romanos going to do following Manzikert?
Well, I think it's a bit more complicated.
When Romanos was made emperor, there was a clear and spoken understanding, that Romanos would respect and protect the interests of the members of the Doukas family already holding imperial titles - Michael VII, Eudokia Makrembolitissa etc. However, by his actions, I think that it's fair to assume that he was actually trying to undo this settlement, and create a new order, and dynasty, with him at its helm. The marginalisation of Eudokia, the continued seclusion of Michael VII from the affairs of government, the exile of John Doukas (the main potential threat on such a plan), and the elevation of his sons with Eudokia to the imperial rank - which was a direct threat on the rights of Michael and his brothers, were all at least worrisome signs about his intentions, and at least personally, I don't think that all these were just misunderstandings - the creation of the co-emperors in particular was a rather clear indication. So, I think we can argue that Romanos himself played a crucial role in creating this political crisis and, and perhaps that he fired the first shots; it was clear the Doukai would react to any move seeming to endanger their position, so he most likely expected that they would react.