Horizon has about $US40 m in cash with strong income from sales...

Horizon has about $US40 m in cash with strong income from sales revenue and results driven by production from Beibu Gulf oil fields. If there is a cr (and i doubt it) it will be to drive exploration and production of former ROC assets in the new company and that will be a good thing.
When you query where Horizon would be without ROC consider the opposite. ROC is largely an exploration company with small production whereas Horizon is an explorer on the cusp of massive production, it has the Stanley wet gas field and a production licence, and construction of its gas pant is underway.. Merge the two companies and you get a company with an income stream and excellent future prospects. It's a future Oil Search in the making and shareholders in both companies will do very well out of it. In anticipation the sp of both companies has been doing very well. Investors have evaluated to new company and are demonstrating their confidence by driving the sp of both ROC and HZN up.

Also note that companies get a premium from the merger, the synergies of the merger create considerable added value,
Please note the following in the Deloitte report:
Microsoft Word - Draft ASX Letter_3Jul2014 v2

1. As calculated in Table 2, ROC shareholders are also receiving a premium as a result of the Proposed Scheme, when compared with the ROC share price prior to the announcement of the Proposed Scheme, although the analysis is subject to the same limitations discussed previously....This implied premium is broadly consistent with the premium implied for Horizon shareholders.  

Just as one could